Electricity (Case Study) (Class 10 Science)

Case-based questions on electric circuits, current, resistance, and power. Real-world applications in household wiring and electrical safety.

Electricity (Case Study) (Class 10 Science)

Case-based questions on electric circuits, current, resistance, and power. Real-world applications in household wiring and electrical safety.

✓ 100% Free ✓ No Login Needed ✓ NCERT / CBSE Aligned ✓ Download as PDF

TL;DR: Case-based questions on electric circuits, current, resistance, and power. Real-world applications in household wiring and electrical safety.

Written & reviewed by the Syllab.in Academic Team (CBSE/NCERT subject experts) · Updated

🤖 Stuck on any question? Ask Syllab's free AI Tutor for a step-by-step explanation — instant, unlimited, no login.

Case-based questions on electric circuits, current, resistance, and power. Real-world applications in household wiring and electrical safety.

Electricity (Case Study) MCQs with Answers & Explanations

Q1. A house has a 5 A fuse and operates at 230 V. A resident connects a 1000 W heater, 500 W oven, and 100 W light simultaneously. Will the fuse blow? (Calculate power consumed)

  1. No, total 1100 W is safe
  2. No, fuses only regulate current
  3. Yes, total 1600 W exceeds fuse capacity ✓ (correct)
  4. Cannot determine without resistance values

Explanation: Total power = 1000 + 500 + 100 = 1600 W. Current I = P/V = 1600/230 = 6.96 A. This exceeds the 5 A fuse rating (which allows 5*230 = 1150 W maximum), so the fuse will blow.

Q2. Three resistors of 6 ohms, 6 ohms, and 12 ohms are connected in a circuit. Two 6-ohm resistors are in parallel, then this combination is in series with the 12-ohm resistor. What is the total resistance?

  1. 24 ohms
  2. 3 ohms
  3. 9 ohms
  4. 15 ohms ✓ (correct)

Explanation: Two 6-ohm resistors in parallel: 1/Rp = 1/6 + 1/6 = 1/3, so Rp = 3 ohms. That 3 ohms is in series with 12 ohms, so the total is 3 + 12 = 15 ohms.

Q3. A copper wire has a resistance of 5 ohms at 20°C. As temperature increases to 100°C, the resistance increases due to thermal motion of electrons. What happens to the conductivity of copper?

  1. Decreases ✓ (correct)
  2. Increases
  3. Remains constant
  4. Becomes zero

Explanation: Conductivity is the inverse of resistivity. As temperature increases, resistivity increases, so conductivity decreases. Higher thermal motion causes more collisions, increasing resistance.

Q4. An ammeter has a low resistance (nearly zero) while a voltmeter has high resistance. Why must an ammeter be connected in series and a voltmeter in parallel?

  1. To prevent voltage drops across ammeter
  2. To ensure accurate measurement of current and voltage respectively ✓ (correct)
  3. To avoid damaging the instruments
  4. There is no specific reason

Explanation: An ammeter in series measures current without affecting the circuit (low resistance means minimal voltage drop). A voltmeter in parallel measures potential difference across components without drawing significant current (high resistance prevents circuit loading).

Q5. A circuit has a 12 V battery, a switch, a 4-ohm resistor, and an ammeter. When the switch is closed, the ammeter reads 2.5 A. What is the internal resistance of the battery?

  1. 0.4 ohms
  2. 1.6 ohms
  3. 0.8 ohms ✓ (correct)
  4. 2.0 ohms

Explanation: Using V = I(R + r): 12 = 2.5(4 + r), so 12 = 10 + 2.5r, giving 2.5r = 2, r = 0.8 ohms.

Q6. A light bulb rated 60 W, 120 V is used in a 240 V circuit with an appropriate series resistor for protection. What is the power consumed by the series resistor?

  1. 20 W
  2. 90 W
  3. 30 W
  4. 60 W ✓ (correct)

Explanation: The bulb needs 120 V at I = 60/120 = 0.5 A. The series resistor takes the other 240 - 120 = 120 V at the same 0.5 A, so its power is P = V x I = 120 x 0.5 = 60 W.

Q7. In a parallel circuit with three identical bulbs rated 100 W each at 230 V, if one bulb burns out, what happens to the brightness of the remaining bulbs?

  1. Remains same ✓ (correct)
  2. Increases
  3. Becomes zero
  4. Decreases

Explanation: In a parallel circuit, each bulb receives the full voltage (230 V) independently. If one bulb burns out, the voltage across others remains 230 V and their current remains the same, so brightness is unchanged.

Q8. A heating element of resistance 10 ohms carries a current of 2 A for 5 minutes. How much heat is produced?

  1. 100 J
  2. 12000 J ✓ (correct)
  3. 6000 J
  4. 1000 J

Explanation: Heat Q = I^2 * R * t = 2^2 * 10 * 300 = 4 * 10 * 300 = 12000 J.

Frequently Asked Questions

What is the difference between an electric fuse and a circuit breaker?

A fuse is a one-time protective device that melts when current exceeds its rating, breaking the circuit. A circuit breaker is a reusable automatic switch that trips when overloaded and can be reset. Fuses provide overcurrent protection but require replacement, while breakers offer convenience and can be switched manually.

Why does a thicker wire have lower resistance than a thin wire of the same material and length?

Resistance is given by R = rho * L / A, where A is the cross-sectional area. A thicker wire has a larger area A, so resistance is inversely proportional to area. More material allows charge carriers more pathways, reducing opposition to current flow.

More Class 10 Science MCQs

🤖 Stuck on any of these? Ask Syllab's free AI Tutor to explain step by step →