Question

(a) The electric power consumed by a device may be calculated by using either of the two expressions P = 12R or P =V2/R . The first expression indicates that it is directly proportional to R whereas the second expression indicates inverse proportionality. How can the seemingly different dependence of P on R in these expressions be explained?
(b) (i) A 100 W electric bulb is connected to 220 V mains power supply. Calculate the strength of the electric current passing through the bulb. (ii) If the same bulb is taken to U.S.A where the main power supply is 110 V, how much electric current will pass through the bulb when connected to mains?​

Answer 1

Answer:

Heya!

In first case where P = I²R, you cannot say that power is directly proportional to R unless current is constant, here power depends on I and R both.

for

P∞R , (I must be constant)

similarly for P = V²/R , you cannot say P is inversely proportional to R unless Voltage is constant.

In second question________________

Power and Voltage are given,

apply formula

P = VI

put the given values, you'll get your answer . it's simple calculation!