Question

a lamp can work on a 50 volt mains taking 2 A. 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

Answer:

Explanation:

V = 50 V  

I = 2 A  

V = IR  

50 = 2(R)  

R = 25 ohm

P = V^2/R = 2500/25 = 100 W

P = 40000/R'  

R' = 400 ohm  

R' = R + R"  

400 = 25 + R"  

R" = 375 ohm