Electricity Important MCQ | Class 10 Science Chapter 11 MCQ Questions

1. Two conducting wires of the same material and of equal lengths and equal diameters are first connected in series and then parallel in a circuit across the same potential difference. The ratio of heat produced in series and parallel combinations would be:

(a) 1 : 2 

(b) 2 : 1 

(c) 1 : 4 

(d) 4 : 1 

Ans. (c) 1 : 4 

Explanation :

As the two conducting wires are of the same material, equal lengths and equal diameters. They will have the same resistance.

Let the resistance of each wire be R and applied potential difference, V. Rseries = R1 + R2

= R + R = 2R 

2. A student plots V-I graphs for three samples of nichrome wire with resistances R1, R2 and R3. Choose from the following statement that holds true of this graph.

(a) R1 = R2 = R3 

(b) R1 > R2 > R3 

(c) R3 > R2 > R1< 

(d) R2 > R1 > R3 

Ans. (d) R2 > R1 > R3 

Explanation :

As it is clear from the graph, the current for A2 conductor is less than A1 and A1 is less than A3 we can say IA2 < IA1 < IA3. We know

If I is less, then R will be more. IA2 < IA1 < IA3 ∴ R2 > R1 > R3.

3. The instrument used for measuring electric current is: 

(a) galvanometer

(b) ammeter 

(c) voltmeter 

(d) potentiometer

Ans. (b) ammeter 

Explanation :

Ammeter is a device used for measuring electric current in amperes.

4. Which of the following does not apply to silver ? 

(a)The resistance provided is directly proportional to its length.

(b) The resistance provided is inversely proportional to the area of cross section.

(C) Their resistivity is in the range 10–8 Ω to 10–6 Ω.

(d) The movement of electrons on their outer most orbital is tightly held together.

Ans. (d) The movement of electrons on their outer most orbital is tightly held together.

Explanation : For a given continuous piece of uniform wire, the resistance is

directly proportional to its length. Thus, silver which is a good conductor of electricity and the resistance in it is directly proportional to its length. Silver is a good conductor of electricity, thus, the resistance provided is inversely proportional to the area of cross section. Silver has resistivity in the range of 10−8Ω to 10−6Ω. Therefore, it is considered as very good conductors. Hence, the statement that does not apply to silver is the movement of electrons on their outer most orbital is tightly held together.

5. R1 and R2 are two resistors and r1 and r2 are equivalent

⇒ r1 = R1 + R2 r2 = R1R2 = r2r1 …(ii)

Now (R1 – R2)2 = (R1 + R2)2 – 4 R1R2 

=r1 2 – 4 r2r1

6. There are three resistors connected in parallel, the resistance of each resistor is 3 ohm. What is the total resistance of all the three resistors ?

(a) 1 Ω 

(b) 6 Ω 

(c) 15 Ω 

(d) 3 Ω 

Ans. (a) 1 Ω 

Explanation :

It is given that the three resistors are connected in parallel and the resistance of each resistor is 3 Ω. Therefore, R1 = R2 = R3 = 3 Ω

From the formula given below, we can calculate the total resistance of all the three resistors:

Hence, the total resistance is 1 Ω.7. The accumulator which is used for the domestic purpose has the electromotive force of 10 V and with an internal resistance of 0.8 Ω is externally charged by 150 V of the direct current power supply using a series resistor 18 Ω. Calculate the terminal voltage of the accumulator during using.

   

(a) 16.8 V 

(b) 17.1 V 

(c) 11.3 V 

(d) 15.9 V

Ans. (d) 15.9 V

 Explanation :

E = V – Ir V = E + Ir

(a) 1 W 

(b) 5 W

(c) 10 W 

(d) 25 W Ans. 

(a) 1 W 

Explanation :

Explanation :

The correct options are: A-2; B-3; C-4; D-1

10. The resistance of the wire when the length of the wire increases two times :

(a) becomes 2 times  

(b)becomes 3 times

(c) becomes 6 times

(d) becomes 4 times 

Ans. (a) becomes 2 times 

Explanation :

The electrical resistance of a wire can be expressed as:

From this relation, it is clear that the resistance is directly proportional to the length and inversely proportional to area of cross-section.

If length becomes 2L, then

11. Which among the following is the correct way of connecting ammeter and voltmeter in the circuit to determine the equivalent resistance of two resistors in series ?

   

(a) Both ammeter and voltmeter in series 

(b) Both ammeter and voltmeter in parallel (c) Ammeter in parallel and voltmeter in series 

(d) Ammeter in series and voltmeter in parallel

Ans. (d) Ammeter in series and voltmeter in parallel 

Explanation :

The correct way of connecting ammeter and voltmeter in the circuit to determine the equivalent resistance of two resistors is connecting ammeter in series and voltmeter in parallel. Ammeter is connecting in series, so that whole current passes through it and voltmeter in parallel to it could measure the complete voltage of the circuit.