NCERT Class X Science Solutions: Chapter 12 – Electricity Part 1

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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)

Image result for ohm law

Ohm Law

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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.