Science
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Chapter 12: Electricity
Class: X
Exercise 7
Question 1
What determines the rate at which energy is delivered by a current?
Answer 1
The electrical power is the rate of work done by electric current and it determines the rate at which energy is delivered by the current. So, the rate at which energy is delivered by a current is the power of the appliance.
Question 2
An electric motor takes 5 A from a 220 V line. Determine the power of the motor and the energy consumed in 2 h.
Answer 2
Power of the electric motor is given by
P = VI
Given,
V = 220 V,
I = 5 A,
t = 2 hours = 7200 seconds
\ P = 220 × 5 = 1100 W
Energy, E = Power × time = P x t
E = 1100 W x 7200 seconds = 7920000 J = 7.92 x 106 J
Hence, the power of the motor is 1100 W and energy consume in 2 hours is 7.92 x 106 J.
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