Electricity · Class 10 Science: 217 MCQs with answers

Q1. No current flows in a circuit when the plug key is open because:

Q2. Define electric current. State and define its SI unit.

Q3. Define potential difference between two points. State and define its SI unit.

Q4. Distinguish between conventional current and electron flow.

Q5. A 6 V battery moves charge through itself. How much energy does every coulomb pick up?

Q6. Name the components needed to make the simplest working circuit that lights a bulb, and state the function of each.

Q7. 1 ohm equals:

Q8. The resistance of a wire is directly proportional to its:

Q9. If the cross-section area of a wire increases, its resistance:

Q10. A device used to change the current in a circuit gradually is a:

Q11. State Ohm's law. Draw (describe) the shape of the V–I graph for an ohmic conductor and state what its slope gives.

Q12. Define resistance of a conductor and define 1 ohm.

Q13. On what factors does the resistance of a uniform metallic wire depend? Write the formula.

Q14. The equivalent of 2 Ω, 3 Ω and 5 Ω in series is:

Q15. The equivalent of two 10 Ω resistors in parallel is:

Q16. In parallel, the branch with the smallest resistance carries the:

Q17. Five 1 Ω resistors in series give:

Q18. Five 1 Ω resistors in parallel give:

Q19. Why is the series arrangement not used for connecting domestic electrical appliances?

Q20. What happens to the total resistance and the current drawn when more resistors are added (a) in series, (b) in parallel?

Q21. Two lamps rated for 220 V are connected in parallel to a 220 V supply. State two advantages of this connection over series.

Q22. 1 kWh equals:

Q23. A fuse is connected in:

Q24. The formula P = V²/R is most convenient when you know:

Q25. A charge of one coulomb passes a point in one second. The current is:

Q26. A torch bulb draws 300 mA. Expressed in amperes this is:

Q27. A current of 2 A flows through a lamp for half a minute. The charge that passes through it is:

Q28. A battery does 24 J of work moving 3 C of charge through a circuit. The potential difference is:

Q29. In a circuit diagram, conventional current is shown leaving the cell from the terminal drawn as:

Q30. A current of 0.2 A flows for 5 minutes. The charge that passes is:

Q31. 10 J of work moves 2 C of charge between two points. The p.d. is:

Q32. A 6 V battery gives every coulomb passing through it:

Q33. How much energy is given to 4 C of charge by a 12 V battery?

Q34. The number of electrons in 1 coulomb of charge is about:

Q35. The same current flows through every part of a simple series loop because:

Q36. The bulb lights the instant the switch closes because:

Q37. In a torch circuit, the correct order along the loop is:

Q38. An ammeter mistakenly connected in parallel across a bulb causes:

Q39. Which quantity is the SAME for the two bulbs when they are connected one after another (series) to a cell?

Q40. In the water analogy of circuits, the pump corresponds to the:

Q41. Why is an ammeter connected in series and made with very low resistance?

Q42. Why is a voltmeter connected in parallel and made with very high resistance?

Q43. A current of 0.5 A is drawn by a filament bulb for 10 minutes. Find the amount of charge that flows through the circuit.

Q44. A charge of 3 C is carried between two points separated by 15 V. What work does that take?

Q45. Explain, using the water analogy, the roles of the cell, potential difference and current in an electric circuit. Then state the exact definitions and units of current and potential difference.

Q46. Draw (describe) a circuit containing a battery of two cells, a plug key, an ammeter, a resistor, and a voltmeter measuring the p.d. across the resistor. Explain the placement of both meters, the consequences of interchanging them, and the direction of the current.

Q47. A conductor carries 0.5 A when 6 V is applied across it. Its resistance is:

Q48. Silver conducts better than copper, yet household wiring is copper. The deciding factor is that silver is:

Q49. A p.d. of 10 V drives 2 A through a conductor. Its resistance is:

Q50. The current through a 30 Ω resistor connected to a 6 V battery is:

Q51. To drive 0.5 A through a 40 Ω element, the required p.d. is:

Q52. If the p.d. across a fixed resistor is halved, the current:

Q53. Two wires of the same material and length; wire B is twice as thick (twice the diameter). Then:

Q54. A wire of resistance 8 Ω is cut into four equal pieces. Each piece has resistance:

Q55. The filament of a glowing bulb does not obey Ohm's law across its range because:

Q56. On an I–V graph (I on the y-axis), the slope equals:

Q57. Of two V–I lines drawn for resistors P and Q (V on y-axis), P's line is steeper. Then:

Q58. The resistance of a metal wire increases when heated because:

Q59. Manganin and constantan are used in standard resistance coils because their resistivity:

Q60. A wire has R = 4 Ω. Another wire of the SAME material with twice the length and twice the area has resistance:

Q61. Which has the HIGHEST resistivity?

Q62. The resistivity of a copper wire 10 m long is ρ. For a copper wire 20 m long of the same thickness, the resistivity is:

Q63. Define resistivity. Why is it called a characteristic property of the material?

Q64. Why are the coils of electric heating devices made of an alloy rather than a pure metal?

Q65. How much current flows through an electric bulb of resistance 1100 Ω when connected to a 220 V supply?

Q66. The V–I graphs of two conductors A and B are drawn with V on the y-axis; A's line is steeper. Which conductor has more resistance, and why?

Q67. Why does the connecting cord of an electric heater not glow while its heating element does?

Q68. Calculate the resistance of a 2 m long nichrome wire of cross-section 10⁻⁶ m², given nichrome's resistivity is 1.1 × 10⁻⁶ Ω·m.

Q69. Describe an experiment to verify Ohm's law. Include the circuit, procedure, observations, the graph, and the conclusion.

Q70. (a) A 9 V battery drives a current through a series circuit containing a rheostat set to 30 Ω. Find the current. (b) The rheostat is now adjusted to 15 Ω. What is the new current? (c) What must the rheostat be set to for a current of 0.9 A? (d) State what this experiment demonstrates about the role of a rheostat.

Q71. Three resistors are joined in parallel across a 12 V battery. The potential difference across the middle one is:

Q72. An old string of fairy lights goes completely dark when a single bulb fails. This tells you the bulbs were connected:

Q73. A 6 Ω and a 12 Ω resistor are joined in parallel. Their equivalent resistance is:

Q74. The equivalent of 4 Ω and 12 Ω in parallel is:

Q75. A 6 Ω and a 3 Ω resistor in parallel are joined in series with a 4 Ω resistor. The total resistance is:

Q76. Through the 3 Ω branch of that pair flows:

Q77. Two bulbs of resistance 10 Ω and 20 Ω in SERIES on a battery: which glows brighter?

Q78. Adding one more resistor in parallel to an existing circuit makes the total resistance:

Q79. Adding one more resistor in series makes the current drawn from the battery:

Q80. To get 5 Ω from two 10 Ω resistors, connect them in:

Q81. To get 15 Ω from 10 Ω and 5 Ω resistors, connect them in:

Q82. Which single value CANNOT be made from two 6 Ω resistors?

Q83. Three 3 Ω resistors: two in parallel, that pair in series with the third. Total:

Q84. An ammeter reads 3 A entering a junction of two branches carrying I₁ and 1.2 A. I₁ is:

Q85. Derive the expression for the equivalent resistance of three resistors connected in series.

Q86. Derive the expression for the equivalent resistance of three resistors connected in parallel.

Q87. Find the equivalent resistance of 5 Ω and 20 Ω connected in parallel, and the current drawn from a 12 V battery connected across them.

Q88. Three resistors of 10 Ω, 20 Ω and 30 Ω are in series across a 12 V battery. Find the current and the p.d. across each resistor.

Q89. A current of 6 A enters a parallel combination of 2 Ω and 4 Ω. Find the current in each branch.

Q90. An appliance converts 500 joules of electrical energy every second. Its power is:

Q91. An electric iron, an electric fan and a tube light all run from the same supply. Which group names the MAIN energy conversion in each correctly?

Q92. The heat produced by 2 A through 10 Ω in 5 s is:

Q93. The power of an appliance drawing 3 A at 220 V is:

Q94. The resistance of a 220 V, 550 W appliance is:

Q95. The current drawn by a 220 V, 440 W appliance is:

Q96. A suitable fuse for a 220 V, 1000 W heater (I ≈ 4.5 A) is:

Q97. A 100 W bulb runs 10 hours. Energy consumed:

Q98. A 1.5 kW geyser runs 40 minutes. Units consumed:

Q99. At ₹5 per unit, a 2 kW heater running 3 hours daily for 10 days costs:

Q100. Two bulbs, 40 W and 60 W, both rated 220 V. Which has more resistance?

Q101. When the voltage across a fixed resistor doubles, the power dissipated becomes:

Q102. The element of a room heater stays red-hot but its copper leads stay cool because the leads have:

Q103. An electric kettle rated 220 V, 2.2 kW draws a current of:

Q104. The energy consumed by a 40 W bulb in 1 minute is:

Q105. Long-distance power lines use high voltage mainly to:

Q106. An MCB differs from a fuse in that it:

Q107. If the current through a heater coil is halved (same coil), the heat produced in the same time becomes:

Q108. Consider these statements about electric current. I. It is the rate of flow of charge. II. Its SI unit is the ampere. III. In a metal the moving charges are electrons. IV. Conventional current flows in the same direction as the electrons. Which statements are correct?

Q109. About how many electrons must pass a point each second to make a current of 1 A? (e = 1.6 × 10⁻¹⁹ C)

Q110. A student says "current and electrons both flow from the negative terminal to the positive one outside the cell". The statement is:

Q111. A lamp lights the instant a switch is closed, even though electrons drift through the wire slower than a walking ant. The explanation is that:

Q112. Saying that a cell is marked "1.5 V" means that it gives every coulomb passing through it:

Q113. A cell goes flat after long use. What has actually stopped is:

Q114. An ammeter must carry the whole current it is measuring. It follows that it is connected in:

Q115. A voltmeter must read the potential difference ACROSS a component. It follows that it is connected in:

Q116. Why would an ammeter of high resistance give a misleading reading?

Q117. Which group correctly pairs each meter with how it is connected and the resistance it should have?

Q118. A current flows because a potential difference pushes charge round a circuit. Which statement best describes what a cell actually supplies?

Q119. Which group lists three quantities that are ALL measured in different units from one another?

Q120. A student connects a voltmeter in series with a bulb instead of across it. The result is that:

Q121. A steady current of 1 A flows for 1 hour. The total charge that passes is:

Q122. If 1.2 × 10²⁰ electrons pass a point in 4 s, the current is about:

Q123. A charge of 2 C moves between two points, gaining 8 J at one and losing all of it in a bulb. The p.d. across the bulb is:

Q124. Assertion: The direction of conventional current is opposite to electron flow. Reason: The convention was fixed before the electron was discovered, assuming positive carriers.

Q125. Two identical cells (1.5 V each) are joined in series (+ of one to − of the next). A voltmeter across the pair reads:

Q126. Two identical cells of 1.5 V each are joined + terminal to + terminal, so that they oppose each other. A voltmeter across the pair reads:

Q127. A wire carries 0.8 A. In 100 s, the number of electrons crossing any section is about:

Q128. A car battery is rated 40 Ah. It can deliver 2 A for:

Q129. Case: In a lab circuit, the ammeter reads 0.25 A before a resistor and a second ammeter reads after it. In the same series loop, the second reading is:

Q130. A student wants to measure both the current through a bulb and the p.d. across it. The correct setup is:

Q131. Which statement about a 9 V battery made of six 1.5 V cells is TRUE?

Q132. Calculate the number of electrons flowing per second through a conductor carrying a current of 2 A.

Q133. (a) How many electrons make one coulomb? Show the calculation. (b) A device passes 6 × 10²⁰ electrons in 40 s. Find the current. (c) If the device works on a 10 V supply, how much energy does it use in that time?

Q134. A student sets up a circuit and reports: 'The bulb glows dimly. When I open the switch the glow disappears. When I add a second cell in series the glow brightens. When I accidentally connected the second cell the opposite way, the bulb went off completely.' Explain each of the four observations using the concepts of closed circuits and potential difference.

Q135. Consider these statements about Ohm's law. I. It states that V is directly proportional to I. II. It holds only at constant temperature. III. Its V–I graph is a straight line through the origin. IV. Every electrical device obeys it. Which statements are correct?

Q136. A filament bulb's V–I graph curves instead of being straight. The reason is that as the current rises:

Q137. Why does the V–I graph of an ohmic conductor pass through the origin as well as being straight?

Q138. Resistivity is found from ρ = RA/l. Its SI unit must therefore be the:

Q139. A copper wire is cut into two equal halves. Which quantity is the SAME for each half as for the original wire?

Q140. Nichrome, not copper, is used for a heating element because nichrome has:

Q141. The same current flows through an electric iron's copper cord and its nichrome element, yet only the element gets hot. The reason is that:

Q142. A nichrome wire is stretched uniformly to 3 times its length. Its resistance becomes:

Q143. A wire of resistance 12 Ω is folded exactly in half (the halves side by side, joined at both ends). The new resistance is:

Q144. The dimensions of wire X: length l, area A. Wire Y (same material): length 2l, area A/2. Then R_Y/R_X =

Q145. A copper wire (ρ = 1.6 × 10⁻⁸ Ω·m), l = 5 m, A = 0.8 × 10⁻⁶ m². Its resistance is:

Q146. A student's V–I data: (2 V, 0.2 A), (4 V, 0.4 A), (6 V, 0.6 A). The resistance is:

Q147. Assertion: A thick copper wire stays cooler than a thin one carrying the same current. Reason: The thick wire's larger area gives it lower resistance, so less heat (I²R) is produced.

Q148. The element of a room heater glows red-hot but its connecting copper wires stay cool because:

Q149. Doubling BOTH the voltage across and the length of a given wire (same thickness, same material) changes the current by a factor of:

Q150. A 0.5 mm² copper wire and a 0.5 mm² nichrome wire of equal length carry equal currents. Which develops the greater p.d. across it?

Q151. Case: A lab has two mystery wires of the same metal. Wire 1: l, area A, resistance 6 Ω. Wire 2 has length 3l and area 2A. Its resistance is:

Q152. Why do bulb filaments usually blow at the instant of switching ON?

Q153. The resistance of an ideal superconductor is:

Q154. For a wire at constant temperature, which graph is a straight line through the origin?

Q155. A wire of resistance 10 Ω is stretched uniformly to twice its original length. Calculate its new resistance.

Q156. Derive the factors governing the resistance of a wire in the form R = ρl/A, explaining physically why R grows with length and shrinks with thickness. Then define resistivity, give its unit, and compare the resistivity classes of conductors, alloys and insulators with one use of each.

Q157. A copper wire has diameter 0.5 mm and resistivity 1.6 × 10⁻⁸ Ω·m. (a) Find the length of this wire needed to make a 10 Ω resistance. (b) If the diameter is doubled, how does the required length change for the same 10 Ω? What does this tell you about practical resistor design?

Q158. Consider these statements about resistors in series. I. The same current flows through every resistor. II. The voltages across them add to the supply voltage. III. The equivalent resistance is larger than the largest resistor. IV. Each resistor has the full supply voltage across it. Which statements are correct?

Q159. Resistors of 3 Ω, 5 Ω and 12 Ω are joined in series. Without calculating, you can say the equivalent resistance must be:

Q160. Resistors of 3 Ω, 5 Ω and 12 Ω are joined in parallel. Without calculating, the equivalent resistance must be:

Q161. Why does one failed bulb in a house not switch off every other appliance?

Q162. Two unequal resistors are joined in series across a battery. Why does the larger one have the larger voltage across it?

Q163. A combination of resistors with a total resistance of 6 Ω is connected to a 12 V battery. The main current drawn from the battery is:

Q164. A 4 Ω resistor is in series with a parallel pair whose combined resistance is 2 Ω, the whole across a 12 V battery. The potential difference across the parallel pair is:

Q165. Two bulbs of resistance 10 Ω and 20 Ω are connected in PARALLEL across a battery. Which glows brighter?

Q166. A wire of resistance R is cut into n equal parts, and all parts are connected in parallel. The equivalent resistance is:

Q167. A 12 Ω wire is cut into three equal parts connected in parallel. The result is:

Q168. Four 2 Ω resistors can produce which of the following equivalents?

Q169. Assertion: In domestic wiring, a short circuit in the toaster does not stop the fans. Reason: Each appliance sits on its own parallel branch across the mains.

Q170. Two resistors give 9 Ω in series and 2 Ω in parallel. The resistors are:

Q171. A battery drives 1 A through two series resistors, dropping 4 V and 8 V across them. Their values are:

Q172. Case: A student needs exactly 1 Ω but has only 2 Ω resistors. The minimum number needed is:

Q173. Case: A hostel corridor has 10 identical lamps in parallel on 220 V, each of resistance 484 Ω. The total current drawn is about:

Q174. If one of those 10 lamps burns out, the current through EACH remaining lamp:

Q175. The total resistance between points A and B: a 2 Ω resistor in series with [4 Ω parallel 4 Ω]:

Q176. Two heaters of resistance R each boil a pot of water in time t when used one at a time. Used TOGETHER in parallel on the same supply, they boil it in about:

Q177. Two heaters of resistance R each boil a pot of water in time t when used one at a time. Connected in SERIES on the same supply, they boil the same pot in about:

Q178. Which arrangement of a 1 Ω, 2 Ω and 3 Ω resistor gives an equivalent CLOSEST to 2 Ω?

Q179. Show how you would connect three resistors, each of 6 Ω, to obtain (i) 9 Ω, (ii) 4 Ω.

Q180. Why do the headlights of a car become slightly dimmer when the starter motor runs?

Q181. With derivations, compare the series and parallel combinations of resistors under the headings: current, potential difference, equivalent resistance, effect of one component failing, and one practical application of each.

Q182. A circuit has a 6 V battery, a 1 Ω resistor in series, and then a parallel pair of 4 Ω and 12 Ω. Calculate (a) the total resistance, (b) the main current, (c) the p.d. across the parallel pair, (d) the current in each branch, and (e) verify that the branch currents add up correctly.

Q183. You are given a box of identical 4 Ω resistors. Explain, with working, how to build: (a) 12 Ω, (b) 1 Ω, (c) 6 Ω, (d) 10 Ω — using as few resistors as possible each time. State the general principles you used.

Q184. Explain fully why parallel wiring is used in homes, and what would actually happen, appliance by appliance, if a house with a 220 V supply were wired in series with a bulb (480 Ω), a fan (240 Ω) and a heater (48 Ω).

Q185. Consider these statements about the heating effect of current. I. The heat produced is proportional to the square of the current. II. Doubling the current gives four times the heat. III. The heat is proportional to the resistance and to the time. IV. Halving the current halves the heat. Which statements are correct?

Q186. A heater carries 4 A through a 20 Ω element for 1 minute. The heat produced is:

Q187. A bulb marked "40 W, 220 V" is run at 220 V. The current it draws is about:

Q188. A 2 kW geyser runs for 45 minutes. The number of units of electricity consumed is:

Q189. An incandescent bulb is filled with an inert gas rather than air because:

Q190. Why must a fuse wire have a LOW melting point and a HIGHER resistance than the circuit wiring?

Q191. Why is an electric fan not said to work by the heating effect, even though its motor does become warm?

Q192. A 60 W and a 100 W bulb (both 220 V-rated) are connected in SERIES to the mains. Which glows brighter?

Q193. A 60 W and a 100 W bulb, both rated 220 V, are connected in PARALLEL to the 220 V mains. Which glows brighter?

Q194. Two identical heating coils (R each) on a fixed supply: connected in parallel they produce heat at rate H₁; in series at rate H₂. H₁/H₂ =

Q195. An electric iron's rating plate says 750 W at 220 V. Heat produced in 10 minutes:

Q196. Assertion: A fuse must be placed in the live wire, not the neutral. Reason: Breaking the live wire disconnects the appliance from the high potential, making it safe to touch.

Q197. A 220 V line has a 5 A fuse. The maximum total power of appliances that can safely run is:

Q198. A bulb rated 220 V, 100 W is run on 110 V. Its power consumption becomes about:

Q199. Case: Riya's home runs a fridge (average 100 W, all 24 h), a TV (100 W for 4 h) and a washing machine (500 W for 1 h) daily. The daily consumption is about:

Q200. An immersion rod raises the temperature of water using H = I²Rt. To heat the same water in HALF the time on the same supply, the rod's resistance must be: