Vardaan Learning Institute

Topic: Electricity

Class: 10 (Science) Type: Bonus Practice Paper Max. Marks: 50
Name:
Date:
SECTION A: OBJECTIVE TYPE QUESTIONS (1 Mark Each)
1. The S.I. unit of electric potential difference is:
  1. Ampere
  2. Volt
  3. Ohm
  4. Joule
2. Which of the following does not represent electrical power in a circuit?
  1. $I^2R$
  2. $IR^2$
  3. $VI$
  4. $V^2/R$
3. Two resistors of resistance 2 $\Omega$ and 4 $\Omega$ are connected in series. The equivalent resistance will be:
  1. 6 $\Omega$
  2. 2 $\Omega$
  3. 4/3 $\Omega$
  4. 0.5 $\Omega$
4. The commercial unit of electrical energy is:
  1. Watt
  2. Watt-hour
  3. Kilowatt-hour (kWh)
  4. Joule
5. What is the relation between Potential difference (V), Current (I) and Resistance (R) according to Ohm's Law?
  1. V = I/R
  2. R = I/V
  3. V = IR
  4. I = VR
6. The device used to measure electric current is:
  1. Ammeter
  2. Voltmeter
  3. Galvanometer
  4. Potentiometer
7. Which of the following is used as a filament in electric bulbs?
  1. Nichrome
  2. Tungsten
  3. Copper
  4. Aluminum
8. To prevent an electric circuit from overloading and short-circuiting, we use a:
  1. Switch
  2. Fuse
  3. Resistor
  4. Socket
9. When two resistors are connected in parallel, the quantity that remains constant across each is:
  1. Current
  2. Potential Difference
  3. Power
  4. Heat
10. The rate of flow of electric charge is known as:
  1. Electric potential
  2. Electric conductance
  3. Electric current
  4. None of these
Directions (Q11-Q14): In the following questions, a statement of assertion (A) is followed by a statement of reason (R). Mark the correct choice as:
  1. Both A and R are true and R is the correct explanation of A.
  2. Both A and R are true but R is not the correct explanation of A.
  3. A is true but R is false.
  4. A is false but R is true.
11. Assertion (A): Tungsten is used for making filaments of electric bulbs.
Reason (R): Tungsten has a very high melting point and high resistivity.
12. Assertion (A): Alloys are commonly used in electrical heating devices like electric irons and toasters.
Reason (R): Alloys do not oxidize (burn) readily at high temperatures and have higher resistivity than constituent metals.
13. Assertion (A): In a series circuit, the current is constant throughout the electric circuit.
Reason (R): In a series circuit, there is only one path for the flow of current.
14. Assertion (A): A fuse wire is always connected in parallel with the mainline.
Reason (R): If a current larger than the specified value flows through the circuit, the fuse wire melts and breaks the circuit.
SECTION B: SHORT ANSWER QUESTIONS (3 Marks Each)
15. Name the factors on which the resistance of a conductor depends.
16. A copper wire of length 2 m and area of cross-section $1.7 \times 10^{-6} m^2$ has a resistance of $2 \times 10^{-2} \Omega$. Calculate the resistivity of copper.
17. Why is the series arrangement not used for domestic circuits? (Give two reasons).
18. An electric bulb is rated 220 V and 100 W. When it is operated on 110 V, the power consumed will be:
19. Calculate the number of electrons constituting one coulomb of charge. ($e = 1.6 \times 10^{-19}$ C).
20. An electric refrigerator rated 400 W operates 8 hours/day. What is the cost of the energy to operate it for 30 days at Rs 3.00 per kWh?
SECTION C: LONG ANSWER QUESTIONS (5 Marks Each)
21. (i) Derive an expression for the equivalent resistance of three resistors $R_1$, $R_2$ and $R_3$ connected in parallel.
(ii) In a circuit, 3 resistors of 5 $\Omega$, 10 $\Omega$ and 30 $\Omega$ are connected in parallel to a 12 V battery. Calculate:
(a) The current through each resistor.
(b) The total current in the circuit.
(c) The total circuit resistance.
22. (i) State Joule's Law of Heating.
(ii) An electric iron of resistance 20 $\Omega$ takes a current of 5 A. Calculate the heat developed in 30 seconds.
(iii) Explain why the cord of an electric heater does not glow while the heating element does.
SECTION D: CASE STUDY (4 Marks)
23. Read the following text and answer the questions:
Electrical resistivity of some substances at $20^\circ C$ is given below:
Silver: $1.60 \times 10^{-8} \Omega m$
Copper: $1.62 \times 10^{-8} \Omega m$
Tungsten: $5.20 \times 10^{-8} \Omega m$
Mercury: $94.0 \times 10^{-8} \Omega m$
Nichrome: $100 \times 10^{-6} \Omega m$

(i) Which among silver and copper is a better conductor? (1 Mark)
(ii) Which material would you advise to use in the heater element of an electric iron? (1 Mark)
(iii) Why are alloys commonly used in electrical heating devices? (2 Marks)
24. Read the following text and answer the questions:
A fuse is an important safety device in electrical circuits. It protects circuits and appliances by stopping the flow of any unduly high electric current. The fuse is placed in series with the device. If a current larger than the specified value flows through the circuit, the temperature of the fuse wire increases. This melts the fuse wire and breaks the circuit.

(i) What is the main function of an electric fuse? (1 Mark)
(ii) Should a fuse be connected in series or parallel with the appliance? (1 Mark)
(iii) Why is tin-lead alloy (solder) used for making fuse wires? (2 Marks)
"All the best!"