NCERT Class X Science Solutions: Chapter 12 – Electricity Part 1 (For CBSE, ICSE, IAS, NET, NRA 2022)

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Question 1:

A piece of wire of resistance R is cut into five equal parts. These parts are then connected in parallel. If the equivalent resistance of this combination is then the ratio is

Answer:

Resistance of a piece of wire is directly proportional to its length. If the piece of wire has a resistance R and the wire is cut into five equal parts.

The resistance of each part

All the five parts are connected in parallel. Hence, equivalent resistance is given as 1

Hence, the option D is correct.

Question 2:

Which of the following terms does not represent electrical power in a circuit?

Answer:

We know that electric power is given by … (i)

So, the option C is correct.

According to Ohm՚s law, … (ii)

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Now putting the value of V from (ii) in (i) , we get

So, the option A is correct.

Now putting the value of I from (ii) in (i) , we get

So, the option D is correct.

Hence, the option B does not represent electrical power in a circuit.

Question 3:

An electric bulb is rated and . When it is operated on , the power consumed will be

  1. 100 W
  2. 75 W
  3. 50 W
  4. 25 W

Answer:

Energy consumed by bulb

Here, and

The resistance of the bulb remains constant if the supply voltage is reduced to . If the bulb is operated on , then the energy consumed by it is given by the expression for power

Hence, the option D is correct.