Question

If the current in the electric bulb decreases by 20% then the power in the bulb decreases by

Answer 1

Power of light bulb is:

$$P = U \cdot I = I^2 \cdot R$$

- The first value of power

where

- U - voltage,

- I - current,

- R - resistance(constant for light bulb)

If we decrease current, power will decrease.

$$I_1 = 0.8 \cdot I$$

Power with lower current:

$$P_1 = 0.64 \cdot I^2 \cdot R$$ $$P_1 = 0.64 \cdot P$$

- value of power if we decrease current