NCERT Solution for Class 10 Science Chapter 12

Electricity

NCERT Books for Session 2022-2023

CBSE Board and UP Board

Intext Questions

Page No-220

Questions No-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.

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Power of the electric motor is given by

P = VI

Where, V = 220 V and I = 5 A

So, Power P = 220 × 5 = 1100 W

Now, the energy consumed = Power × time

Where, P = 1100 W

t = 2 hours = 2 × 60 × 60 seconds = 7200 seconds

So, the energy consumed E = 1100 × 7200 J = 7920000 J

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Here, I = 5 A, V = 220 V, t = 2h = 7,200 s

Power, P = V I = 220 x 5 = 1100 W

Energy consumed = P x t = 1100 W x 7200 s = 7,920,000 J

Given, Electric current (I) = 5A,

Potential difference (V) = 220V,

Time (t) = 2h = 2 x 60 x 60 s = 7200 s

Power (P) =?

Energy consumed =?

We know that, P = VI = 220V × 5A = 1100W

We know that energy consumed by the electric appliance = P × t

⇒ Energy consumed = 1100 W × 7200 s = 7920000 J = 7.92 × 10

^{6}JPower Calculation:

The power (P) of an electrical device can be calculated using the formula:

P = 1 . V

Where:

» P is the power (in watts),

» I is the current (in amperes),

» V is the voltage (in volts).

Given:

I = 5 A (current)

V = 220 V (voltage)

substitute these values into the formula:

P = 5 A . 220V

P = 1100 W

So, the power of the motor is 1100W.

Energy Consumption Calculation:

The energy (E) consumed by the motor can be calculated using the formula:

E = P . t

where:

» E is the energy consumed (in watt-hours),

» P is the power (in watts),

» t is the time (in hours).

Given:

P = 1100 W (power)

t = 2h (time)

Substitute these values into the formula:

E = 1100 W . 2 h

E = 2200 Wh

So, the energy consumed by the motor in 2 hours is 2200 Wh or 2.2 kWh.