Class 10 Science (NCERT)

1. The SI unit of electric current is:

• A. Volt
• B. Joule
• C. Ampere
• D. Coulomb

2. The SI unit of electric charge is:

• A. Ampere
• B. Coulomb
• C. Ohm
• D. Watt

3. How many electrons constitute a charge of 1 Coulomb?

• A. 6 × 10^18
• B. 1.6 × 10^-19
• C. 6 × 10^23
• D. 1.6 × 10^19

4. Electric current is measured using which instrument connected in series?

• A. Voltmeter
• B. Galvanometer
• C. Ammeter
• D. Rheostat

5. The potential difference between two points is measured using which instrument connected in parallel?

• A. Ammeter
• B. Voltmeter
• C. Rheostat
• D. Multimeter

6. The work done in moving a unit charge from one point to another in an electric circuit is defined as:

• A. Electric Current
• B. Electric Power
• C. Potential Difference
• D. Resistance

7. According to Ohm's Law, at constant temperature, current flowing through a metallic wire is directly proportional to:

• A. Its resistance
• B. Its length
• C. Potential difference across its ends
• D. Area of cross-section

8. The SI unit of electrical resistance is:

• A. Volt
• B. Ohm (Ω)
• C. Ampere
• D. Ohm-meter

9. The resistance of a conductor is directly proportional to its:

• A. Area of cross-section
• B. Length (l)
• C. Shape
• D. Volume

10. If the area of cross-section of a wire is doubled, its resistance becomes:

• A. Doubled
• B. Halved
• C. Four times
• D. Unchanged

11. The SI unit of electrical resistivity (ρ) is:

• A. Ohm
• B. Ohm / meter
• C. Ohm-meter (Ω·m)
• D. Volt / meter

12. Which of the following material has the lowest electrical resistivity and is the best conductor?

• A. Copper
• B. Silver
• C. Aluminum
• D. Iron

13. Nichrome is an alloy commonly used in heating elements because:

• A. It has low resistance and low melting point
• B. It has high resistivity and does not oxidize (burn) easily at high temperatures
• C. It is very cheap and lightweight
• D. It exhibits zero resistance at room temperature

14. When three resistors of resistances R1, R2, and R3 are connected in series, the equivalent resistance (Rs) is:

• A. 1/R1 + 1/R2 + 1/R3
• B. R1 + R2 + R3
• C. (R1 × R2 × R3) / (R1 + R2 + R3)
• D. R1 - R2 - R3

15. When resistors are connected in parallel, which quantity remains the same across each resistor?

• A. Current
• B. Potential Difference
• C. Resistance
• D. Heat generated

16. Three resistors of 2 Ω, 3 Ω, and 6 Ω are connected in parallel. Their total equivalent resistance (Rp) is:

• A. 11 Ω
• B. 1 Ω
• C. 2 Ω
• D. 0.5 Ω

17. Domestic electric circuits are always wired in parallel rather than series because:

• A. In parallel, if one appliance fails, others continue working independently
• B. Series wiring requires thicker copper wires
• C. Parallel wiring increases total resistance
• D. In series, voltage across each appliance increases

18. According to Joule's Law of Heating, the heat (H) generated in a resistor is given by the formula:

• A. H = I × R × t
• B. H = I^2 × R × t
• C. H = V × I^2 × t
• D. H = I × R^2 × t

19. Which metal is almost exclusively used for filaments of electric bulbs due to its very high melting point (~3380 °C)?

• A. Copper
• B. Tungsten
• C. Aluminum
• D. Iron

20. Electric bulbs are usually filled with chemically inactive gases like:

• A. Oxygen and Hydrogen
• B. Nitrogen and Argon
• C. Carbon dioxide and Helium
• D. Chlorine and Fluorine

21. An electric fuse is a safety device connected in:

• A. Parallel with live wire
• B. Series with live wire
• C. Series with neutral wire
• D. Parallel with earth wire

22. The rate at which electrical energy is consumed in an electric circuit is called:

• A. Electric Current
• B. Potential Difference
• C. Electric Power
• D. Resistance

23. The SI unit of electric power is:

• A. Joule
• B. Watt (W)
• C. Kilowatt-hour
• D. Ampere

24. Commercial unit of electrical energy is kilowatt-hour (kWh), commonly called 'unit'. 1 kWh is equal to:

• A. 3.6 × 10^5 J
• B. 3.6 × 10^6 J
• C. 1.6 × 10^6 J
• D. 36 × 10^6 J

25. An electric heater rated 1000 W operates on a 220 V line. The current drawn by the heater is approximately:

• A. 4.55 A
• B. 2.2 A
• C. 10 A
• D. 0.22 A

26. If the length of a wire is stretched to double its original length keeping volume constant, its new resistance becomes:

• A. 2 times
• B. 4 times
• C. Half
• D. 8 times

27. A variable resistor used in circuits to change current without changing voltage source is called a:

• A. Galvanometer
• B. Rheostat
• C. Voltmeter
• D. Transformer

28. Two electric bulbs rated (220 V, 100 W) and (220 V, 60 W) are connected in parallel to a 220 V supply. Which bulb draws more current?

• A. 60 W bulb
• B. 100 W bulb
• C. Both draw equal current
• D. Neither draws current

29. Which mathematical formula correctly represents electric power?

• A. P = V × I
• B. P = I^2 × R
• C. P = V^2 / R
• D. All of the above

30. When a wire of resistance R is cut into 5 equal parts and connected in parallel, the equivalent resistance R' gives a ratio R/R' equal to:

• A. 1/25
• B. 1/5
• C. 5
• D. 25