Question

Out of 60W and 40W lamps , which one has higher electrical resistance when in use. Give reason.
PLEASE HELP ME IN THIS QUESTION..​

Answer 1

Answer:

Hence, the resistance of the bulb of 60W is greater.

Explanation:

Let the potential difference used by the bulbs be 'V' . And their usage of current be I.

Here the two bulbs are given.

Let us calculate the resistance of each of them separately.

(i) 60 W

Let the resistance of this bulb be R'.

Here, watt is the symbol of Power. Then,

Power = V × I

60W = VI

By ohm's law we know that,

R = V/I

V = IR

Here, its resistance = R'.

=> 60W = IR' × I

=> 60VI = IR' × I

=> 60V = IR'

=> 60× V/I = R'

=> 60R = R'

Hence, the resistance of this bulb = R' = 60R

(ii) 40 W

Let the resistance of this bulb be R".

Here, watt is the symbol of Power. Then,

Power = V × I

40W = VI

By ohm's law we know that,

R = V/I

V = IR

Here, its resistance = R'.

=> 40W = IR" × I

=> 40VI = IR" × I

=> 40V = IR"

=> 40× V/I = R"

=> 40R = R"

Hence, the resistance of this bulb = R" = 40R

On comparing both 60R and 40R, we get,

60R > 40R

Hence, the resistance of the bulb of 60W is greater.