Basic Electrical and Electronics Engineering: 30 flashcards
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1. What is electric current and what is its unit?
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Current is the rate of flow of electric charge, measured in amperes (A).
2. Define voltage (potential difference) and give its unit.
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Voltage is the potential difference that drives current through a circuit; it is measured in volts (V).
3. What is resistance and what is its unit?
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Resistance is the opposition to the flow of current, measured in ohms ($\Omega$).
4. State Ohm's law.
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For a conductor at constant temperature, $V = IR$ — voltage is directly proportional to current.
5. What distinguishes an ohmic conductor from a non-ohmic one?
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Ohmic conductors give a straight $V$–$I$ graph (constant resistance); non-ohmic ones (diodes, filament lamps) do not.
6. How do you find equivalent resistance in a series circuit?
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$R_{eq} = R_1 + R_2 + \dots$ — resistances simply add up.
7. How do you find equivalent resistance in a parallel circuit?
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$\frac{1}{R_{eq}} = \frac{1}{R_1} + \frac{1}{R_2} + \dots$ — reciprocals add up.
8. Why is house wiring done in parallel?
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So each appliance gets the full supply voltage and can be switched on or off independently.
9. State Joule's law for electrical power.
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$P = VI = I^2R = \frac{V^2}{R}$ — the rate of energy dissipation in a component.
10. In what unit is electrical energy billed?
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Kilowatt-hours (kWh), where $E = Pt$.
11. Write the formula for resistance of a wire in terms of its material and dimensions.
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$R = \rho \frac{L}{A}$, where $\rho$ is resistivity, $L$ is length, and $A$ is cross-sectional area.
12. What is resistivity and how does it vary with material?
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Resistivity $\rho$ is a material property; copper has low $\rho$ (good conductor), nichrome has high $\rho$ (heater coils), rubber has very high $\rho$ (insulator).
13. What is the key property of a diode?
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A diode conducts in one direction only — used for rectification of AC to DC.
14. When is a p-n junction forward biased?
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When the positive terminal of the supply is connected to the p-side of the junction.
15. How many diodes does a bridge rectifier use and what does it achieve?
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Four diodes, achieving full-wave rectification of AC.
16. Name the three terminals of a transistor.
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Emitter, base, and collector.
17. What are the two main functions of a transistor?
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It works as an amplifier or as a switch — the basis of digital logic.
18. Distinguish AC from DC.
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AC reverses direction periodically (50 Hz in India); DC flows in one direction only.
19. What is the function of a transformer?
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It steps AC voltage up or down for efficient transmission.
20. What does a fuse do?
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It melts when current exceeds a safe value, protecting the circuit from damage.
21. Differentiate active and passive components.
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Active components (diodes, transistors) can amplify or switch signals; passive ones (resistors, wires) cannot.
22. Why does a filament bulb's resistance change with temperature?
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For most metals, resistance increases with temperature; a hot filament has much higher resistance than a cold one.
23. What is the function of a circuit breaker?
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It trips on overcurrent, protecting wiring from overheating.
24. What does a phone charger do electrically?
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It converts AC from the wall into DC for the battery using rectification.
25. What is an integrated circuit?
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A chip that packs millions of transistors on a single silicon die.
26. What is EMF and what is its unit?
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Electromotive force is the push provided by a battery or supply, measured in volts (V).
27. What happens to current if you double the voltage across a fixed resistor?
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The current doubles, since $I = V/R$ at constant temperature.
28. What happens to current if you double the resistance at constant voltage?
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The current halves, since $I = V/R$.
29. Why does a filament bulb glow?
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Its high resistance dissipates electrical energy as heat and light via $P = I^2R$.
30. What is the frequency of AC in India?
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50 Hz.
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