Electricity Part 4: MCQs (Q76–Q100)
⚡ Electricity – MCQs (Class 10 Science, NCERT)
🔹 Part 4: Questions 76–100
Q76. A household consumes 250 units of electricity in a month. Energy consumed in joules is:
A) 9 × 10⁷ J
B) 9 × 10⁸ J
C) 9 × 10⁹ J
D) 9 × 10¹⁰ J
Correct Answer: C) 9 × 10⁹ J
Explanation:
- 1 unit = 1 kWh = 3.6 × 10⁶ J.
- 250 units = 250 × 3.6 × 10⁶ = 9 × 10⁸ J. ✅ Correct answer is B (correction).
Q77. The resistance of a wire is R. Its resistance when diameter is doubled (length constant):
A) R/4
B) R/2
C) 2R
D) 4R
Correct Answer: A) R/4
Explanation:
- R = ρL/A. If diameter doubles, area ∝ d² → becomes 4 times.
- New R = R/4. ✅
Q78. Which device works on heating effect of current?
A) Transformer
B) Electric heater
C) Generator
D) Electric motor
Correct Answer: B) Electric heater
Explanation:
- ✅ Heating effect is used in heaters, toasters, irons.
Q79. Which statement is true for parallel circuits?
A) Current same, voltage divides
B) Voltage same, current divides
C) Both same
D) Both divide
Correct Answer: B) Voltage same, current divides
Explanation:
- ✅ In parallel → Potential difference across each branch is same.
Q80. In domestic circuits, appliances are connected in:
A) Series
B) Parallel
C) Combination
D) Sometimes series
Correct Answer: B) Parallel
Explanation:
- ✅ Parallel → Each gets full voltage & independent control.
Q81. Electric current is measured in:
A) Watt
B) Ampere
C) Coulomb
D) Ohm
Correct Answer: B) Ampere
Explanation:
- ✅ 1 A = 1 C/s.
Q82. The SI unit of potential difference is:
A) Ohm
B) Volt
C) Watt
D) Ampere
Correct Answer: B) Volt
Explanation:
- ✅ V = W/Q → unit = J/C = volt.
Q83. A fuse wire is made of:
A) High resistivity, low melting point
B) Low resistivity, high melting point
C) High resistivity, high melting point
D) Low resistivity, low melting point
Correct Answer: A) High resistivity, low melting point
Explanation:
- ✅ Quickly melts & breaks circuit when current exceeds safe value.
Q84. The commercial unit of electrical energy is:
A) Joule
B) Kilowatt-hour
C) Watt
D) Ampere-hour
Correct Answer: B) Kilowatt-hour
Explanation:
- ✅ kWh is practical unit for billing.
Q85. A 220 V heater of 1000 W is used for 2 hours. Energy consumed is:
A) 1 kWh
B) 2 kWh
C) 3 kWh
D) 4 kWh
Correct Answer: B) 2 kWh
Explanation:
- E = P × t = 1000 × 2 h = 2000 Wh = 2 kWh. ✅
Q86. In series circuit, total resistance is:
A) Sum of individual resistances
B) Less than smallest
C) Reciprocal sum
D) Zero
Correct Answer: A) Sum of individual resistances
Explanation:
- ✅ R_eq = R₁ + R₂ + …
Q87. In parallel circuit, total resistance is:
A) Sum of resistances
B) Less than smallest resistance
C) Equal to largest resistance
D) Equal to smallest resistance
Correct Answer: B) Less than smallest resistance
Explanation:
- ✅ 1/R = 1/R₁ + 1/R₂ + … → always less than smallest.
Q88. A 40 W bulb consumes energy in 1 hour equal to:
A) 40 J
B) 144,000 J
C) 3600 J
D) 400 J
Correct Answer: B) 144,000 J
Explanation:
- E = 40 × 3600 = 144,000 J. ✅
Q89. The electrical resistivity of insulators is:
A) Very high
B) Very low
C) Zero
D) Moderate
Correct Answer: A) Very high
Explanation:
- ✅ Insulators resist current strongly.
Q90. Which law relates current, potential difference and resistance?
A) Joule’s law
B) Ohm’s law
C) Newton’s law
D) Kirchhoff’s law
Correct Answer: B) Ohm’s law
Explanation:
- ✅ V = IR.
Q91. The device which converts chemical energy into electrical energy is:
A) Generator
B) Solar cell
C) Electric cell
D) Transformer
Correct Answer: C) Electric cell
Explanation:
- ✅ Electric cell → Battery.
Q92. The device which converts electrical energy into mechanical energy is:
A) Motor
B) Generator
C) Transformer
D) Fuse
Correct Answer: A) Motor
Explanation:
- ✅ Motor works on magnetic effect.
Q93. If voltage is doubled and resistance halved, current becomes:
A) Same
B) Double
C) Four times
D) Half
Correct Answer: C) Four times
Explanation:
- I = V/R → New I = (2V)/(R/2) = 4V/R = 4I. ✅
Q94. For metals, resistivity:
A) Increases with temperature
B) Decreases with temperature
C) Independent of temperature
D) Zero
Correct Answer: A) Increases with temperature
Explanation:
- ✅ More collisions of electrons at higher temperature.
Q95. Nichrome is used as heating element because it has:
A) Low resistivity, low melting point
B) High resistivity, high melting point
C) Low resistivity, high melting point
D) High resistivity, low melting point
Correct Answer: B) High resistivity, high melting point
Explanation:
- ✅ Durable under heating effect.
Q96. Which law explains heating effect of current?
A) Ohm’s law
B) Joule’s law
C) Newton’s law
D) Ampere’s law
Correct Answer: B) Joule’s law
Explanation:
- ✅ H = I²Rt.
Q97. The slope of I–V graph gives:
A) Resistance
B) Conductance
C) Power
D) Voltage
Correct Answer: B) Conductance
Explanation:
- ✅ I–V slope = I/V = 1/R = Conductance.
Q98. A bulb marked 60 W, 220 V. Current drawn is:
A) 0.27 A
B) 0.5 A
C) 1 A
D) 2 A
Correct Answer: A) 0.27 A
Explanation:
- I = P/V = 60/220 ≈ 0.27 A. ✅
Q99. If resistance is doubled and voltage kept constant, power is:
A) Doubled
B) Halved
C) Same
D) Zero
Correct Answer: B) Halved
Explanation:
- P = V²/R. If R doubles → P halves. ✅
Q100. In domestic supply, normal voltage is:
A) 110 V
B) 220 V
C) 440 V
D) 1000 V
Correct Answer: B) 220 V
Explanation:
- ✅ In India, mains supply is 220 V.
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