⚡ Electricity – MCQs (Class 10 Science, NCERT)

🔹 Part 2: Questions 26–50

Q26. Which physical quantity is equal to the slope of V–I graph?

A) Resistance
B) Current
C) Potential difference
D) Power

Correct Answer: A) Resistance

Explanation:

• ✅ A) From Ohm’s law: V = IR → slope = V/I = R.
• B) Current → Not slope.
• C, D → Wrong quantities.

Q27. A wire has resistance R. If its length is doubled and area halved, its resistance becomes:

A) R/4
B) R
C) 4R
D) 2R

Correct Answer: C) 4R

Explanation:

• R = ρL/A. New R’ = ρ(2L)/(A/2) = ρ(4L/A) = 4R. ✅

Q28. The unit of resistivity is:

A) Ω
B) Ω m
C) Ω/m
D) Ω cm²

Correct Answer: B) Ω m

Explanation:

• ✅ B) Resistivity (ρ) = RA/L → Ω·m.

Q29. The reciprocal of resistance is called:

A) Conductance
B) Capacitance
C) Inductance
D) Potential

Correct Answer: A) Conductance

Explanation:

• ✅ A) Conductance (G) = 1/R, unit Siemens.

Q30. A conductor carries 2 A current. In 5 s, charge passing through is:

A) 2 C
B) 5 C
C) 7 C
D) 10 C

Correct Answer: D) 10 C

Explanation:

• Q = It = 2 × 5 = 10 C. ✅

Q31. The electrical energy consumed in 1 hour by a device of 100 W power is:

A) 100 J
B) 3600 J
C) 36,000 J
D) 360,000 J

Correct Answer: D) 360,000 J

Explanation:

• E = P × t = 100 × 3600 = 3.6 × 10⁵ J. ✅

Q32. Which of the following graphs represents Ohm’s law correctly?

A) Straight line through origin
B) Straight line not through origin
C) Parabola
D) Hyperbola

Correct Answer: A) Straight line through origin

Explanation:

• ✅ A) V ∝ I → linear relation.
• B, C, D → Incorrect.

Q33. Resistance of a wire at 20 °C is 5 Ω. At higher temperature, it will be:

A) Less than 5 Ω
B) Equal to 5 Ω
C) More than 5 Ω
D) Zero

Correct Answer: C) More than 5 Ω

Explanation:

• ✅ C) Metals → Resistance increases with temperature.

Q34. Which combination of resistors gives minimum resistance?

A) All in series
B) All in parallel
C) One in series, others in parallel
D) Random

Correct Answer: B) All in parallel

Explanation:

• ✅ B) Parallel → Equivalent R less than smallest resistor.

Q35. Two resistors of 6 Ω each in parallel give equivalent resistance:

A) 3 Ω
B) 6 Ω
C) 12 Ω
D) 2 Ω

Correct Answer: A) 3 Ω

Explanation:

• 1/R = 1/6 + 1/6 = 2/6 → R = 3 Ω. ✅

Q36. An electric bulb is marked 220 V, 100 W. Its resistance is:

A) 220 Ω
B) 484 Ω
C) 22 Ω
D) 2.2 Ω

Correct Answer: B) 484 Ω

Explanation:

• R = V²/P = (220²)/100 = 484 Ω. ✅

Q37. If 1 kWh costs ₹5, the cost of 5 units of electricity is:

A) ₹20
B) ₹25
C) ₹15
D) ₹30

Correct Answer: B) ₹25

Explanation:

• 5 units = 5 kWh. Cost = 5 × 5 = ₹25. ✅

Q38. The resistance of a conductor is 2 Ω. Current 3 A flows for 2 minutes. Heat produced is:

A) 1080 J
B) 2160 J
C) 720 J
D) 540 J

Correct Answer: A) 1080 J

Explanation:

• H = I²Rt = (3²)(2)(120) = 1080 J. ✅

Q39. The heating effect of current is used in:

A) Electric bell
B) Electric heater
C) Generator
D) Electric motor

Correct Answer: B) Electric heater

Explanation:

• ✅ B) Heaters rely on I²Rt heating.

Q40. A fuse wire should have:

A) High resistance and high melting point
B) Low resistance and high melting point
C) High resistance and low melting point
D) Low resistance and low melting point

Correct Answer: C) High resistance and low melting point

Explanation:

• ✅ C) Fuse melts quickly with excess current.

Q41. The SI unit of electric charge is:

A) Ampere
B) Coulomb
C) Joule
D) Watt

Correct Answer: B) Coulomb

Explanation:

• ✅ B) 1 C = charge carried by 1 A in 1 s.

Q42. The instrument used to measure potential difference is:

A) Ammeter
B) Voltmeter
C) Galvanometer
D) Ohmmeter

Correct Answer: B) Voltmeter

Explanation:

• ✅ B) Voltmeter → Connected in parallel across circuit element.

Q43. The potential difference across 5 Ω resistor carrying 2 A current is:

A) 2 V
B) 5 V
C) 10 V
D) 20 V

Correct Answer: C) 10 V

Explanation:

• V = IR = 2 × 5 = 10 V. ✅

Q44. A 220 V appliance consumes 1100 W power. Current drawn is:

A) 2 A
B) 5 A
C) 10 A
D) 20 A

Correct Answer: B) 5 A

Explanation:

• I = P/V = 1100/220 = 5 A. ✅

Q45. The relation between electric power, current and resistance is:

A) P = I²R
B) P = V²/R
C) P = VI
D) All of these

Correct Answer: D) All of these

Explanation:

• ✅ D) All formulas are correct: from V = IR.

Q46. A wire of resistance 10 Ω is doubled in length. Its new resistance is:

A) 10 Ω
B) 20 Ω
C) 30 Ω
D) 40 Ω

Correct Answer: D) 40 Ω

Explanation:

• R’ = ρ(2L)/(A/2) = 4R = 40 Ω. ✅

Q47. The resistance of ideal voltmeter is:

A) Zero
B) Very low
C) Very high
D) Infinity

Correct Answer: D) Infinity

Explanation:

• ✅ D) Infinite resistance → No current drawn.

Q48. The resistance of ideal ammeter is:

A) Zero
B) Very high
C) Infinity
D) Moderate

Correct Answer: A) Zero

Explanation:

• ✅ A) Zero resistance → No voltage drop.

Q49. Which of the following has negative temperature coefficient of resistance?

A) Copper
B) Silver
C) Carbon
D) Aluminium

Correct Answer: C) Carbon

Explanation:

• ✅ C) Resistance of semiconductors decreases with temperature.

Q50. Electric energy consumed =

A) VIt
B) I²Rt
C) V²t/R
D) All of these

Correct Answer: D) All of these

Explanation:

• ✅ D) All relations correct from Ohm’s law.

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