WORKSHEET – CHAPTER 7: ELECTRICITY

SECTION A – MULTIPLE CHOICE QUESTIONS (20 MCQs)

  1. SI unit of electric charge is:
     a) Ampere
     b) Coulomb
     c) Volt
     d) Ohm

  2. The current flowing in a conductor is given by:
     a) I = V/R
     b) I = R/V
     c) I = QR
     d) Q = IR

  3. The device used to measure current is:
     a) Generator
     b) Ammeter
     c) Voltmeter
     d) Galvanometer

  4. Resistance of a conductor depends on:
     a) Length
     b) Area
     c) Temperature
     d) All of these

  5. Ohm’s law holds only when:
     a) Temperature is constant
     b) Voltage is constant
     c) Resistance is zero
     d) Current is zero

  6. If the voltage is doubled, current becomes:
     a) Half
     b) Double
     c) Zero
     d) Infinite

  7. The total resistance in series is:
     a) Minimum
     b) Maximum
     c) Product
     d) Zero

  8. In parallel combination, voltage across each resistor is:
     a) Different
     b) Same
     c) Half
     d) Double

NUMERICAL MCQs
  1. A charge of 20 C flows through a wire in 5 s. Current is:
     a) 2 A
     b) 4 A
     c) 5 A
     d) 10 A

  2. If R = 10 Ω and I = 2 A, potential difference is:
     a) 5 V
     b) 10 V
     c) 20 V
     d) 40 V

  3. A resistor of 12 Ω is connected to 6 V. Power consumed =
     a) 1 W
     b) 3 W
     c) 6 W
     d) 12 W

  4. A wire has resistance 20 Ω. If length is doubled, new resistance is:
     a) 10 Ω
     b) 20 Ω
     c) 40 Ω
     d) 80 Ω

  5. A 60 W bulb runs for 5 hours. Energy consumed =
     a) 300 Wh
     b) 0.3 kWh
     c) Both a & b
     d) None

  6. A heater draws 10 A from 220 V. Power =
     a) 220 W
     b) 2200 W
     c) 22 W
     d) 22 kW

 Conceptual MCQs
  1. A thick wire has:
     a) High resistance
     b) Low resistance
     c) No resistance
     d) Zero resistance

  2. In an electric circuit electrons flow from:
     a) + to –
     b) – to +
     c) Both ways
     d) No flow

  3. SI unit of resistivity is:
     a) Ωm
     b) Ω/cm
     c) Ω/m²
     d) Ω/m

  4. When resistors are in parallel:
     a) Effective resistance decreases
     b) Effective resistance increases
     c) No change
     d) Impossible

  5. Electric fuse works on:
     a) Heating effect
     b) Magnetic effect
     c) Chemical effect
     d) None

  6. An electric iron of 1000 W is used for 1 hour. Energy consumed is:
     a) 1 kWh
     b) 1000 kW
     c) 1000 J
     d) 3600 kWh

SECTION B – ASSERTION & REASON (10 Questions)

  1. A: Current is directly proportional to voltage.
     R: Ohm’s law states V = IR.

  2. A: In parallel combination, current divides.
     R: Voltage remains same across parallel branches.

  3. A: Metals are good conductors of electricity.
     R: They have free electrons.

  4. A: Resistivity of a material is constant.
     R: It depends only on length and area.

  5. A: Heating effect is more in thin wire.
     R: Thin wire has higher resistance.

  6. A: Fuse wire melts due to heating effect.
     R: Fuse wire has low melting point.

  7. A: Electric power can be written as VI.
     R: It is the rate of doing electric work.

  8. A: In a metallic conductor, current is due to electrons.
     R: Electrons move from high potential to low potential.

  9. A: Resistance increases with temperature.
     R: Resistivity increases with temperature for metals.

  10. A: A 1 kW heater consumes 1 unit per hour.
     R: 1 unit = 1 kWh.

SECTION C – ONE-WORD / VERY SHORT ANSWERS (10)

  1. Define electric current.
  2. Write SI unit of resistance.
  3. State Ohm’s law.
  4. Write formula for resistivity.
  5. What is electric power?
  6. Define 1 kWh.
  7. What is the SI unit of charge?
  8. Write unit of potential difference.
  9. What is the purpose of fuse?
  10. What is meant by electric circuit?

SECTION D – SHORT ANSWER QUESTIONS (8)

  1. Explain how resistance depends on length and area of conductor.
  2. A wire draws 2A current when connected to 6V. Calculate resistance.
  3. Why are household connections done in parallel?
  4. Derive the expression for power P = I²R.
  5. Draw labeled circuit diagram to verify Ohm’s law.
  6. What is difference between resistance and resistivity?
  7. Three resistors 2Ω, 3Ω and 6Ω are connected in series. Find equivalent resistance.
  8. 2 identical resistors of 4Ω are connected in parallel. Find effective resistance.

SECTION E – LONG ANSWER QUESTIONS (5)

Q1. (Complete Numerical – 5 Marks)

A 100 W bulb is used for 6 hours per day for one month (30 days).

(a) Calculate total energy consumed in kWh.
 (b) If cost of 1 unit = ₹7, find monthly bill.
 (c) If bulb is replaced with 10 W LED, find percentage saving.

Q2. (Case-Based Series & Parallel – 5 Marks)

Riya wants to connect three bulbs rated 40W, 40W, 40W.

(a) Draw circuit diagram for series and parallel.
 (b) Which combination gives more brightness? Why?
 (c) Find equivalent resistance in both cases if each bulb = 6Ω.
 (d) Which combination is used in homes? Give 2 reasons.

Q3. (Ohm’s Law Derivation + Numerical)

(a) State and explain Ohm’s law.
 (b) Draw V–I graph for an ohmic conductor.
 (c) A conductor has resistance 5Ω. Find current if V = 20V.
 (d) If length is doubled, what happens to resistance? Explain.

Q4. (Heating Effect of Current – 5 Marks)

(a) Derive H = I²Rt (Joule’s law).
 (b) Explain why fuse wire melts.
 (c) An electric heater of 1000 W works for 30 min. Calculate heat produced.
 (d) Why does thick wire produce less heat?

Q5. (Super HOTS – Full Concept Question)

A circuit consists of a 12V battery and three resistors 4Ω, 6Ω, 12Ω connected in parallel.

(a) Draw a neat diagram.
 (b) Calculate total resistance.
 (c) Calculate total current.
 (d) Calculate current through each resistor.
 (e) State one advantage of parallel circuits over series.

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