Question

a lamp can work on a 50 volt mains taking 2 amp. what value of the resistance must be connected in series with it so that it can be operated from 200 volt mains giving the same power.

Answer 1

First, find power
P =VI
P= 50*2 = 100W
Now, we know the value of power.

It is asked to find the resistance when potential difference is 200V and Power is same(I.e 100 W)
When connected in series,
P= Vsquare/R
Vsquare/P = R
200/100 = R
Therefore R = 2ohm
A resistance of 2 ohm is required so that we get the same power and 220v potential difference



Yrr ye physics ka chapter sahi mein difficult hai. I am struggling with this chapter :(

Answer 2

Answer:

75 ohm resistor must be connected, in order to get the same power frim the lamp.

Explanation:

See, We are given A lamp which operates on 50v and 2A,

so Power of the lamp = V × I = 50v × 2A = 100 watt

Now, we have the power of the lamp, we have to make sure the power remain same even in 200v line.

V = 200v

I = 2 amp

R(total) = V/I = 200/2 = 100 ohm

Total resistance of circuit = 100 ohm

But lamp have resistance of 25 ohm

R(s) = R1 + R2

100 = R1 + 25

R1 = 100 -25

R1 = 75 ohm.