Question

26. Two lamps, one rated 40W at 220 V and the other 100 W at 220 V,are cont acted in parallel to the
electric supply at 220 V
A. Draw a circuit diagram to show the connections
B. calculate the current drawn from the electric supply
C. calculate the total energy consumed by the two lamps together when th y operate for one hour.
OR​

Answer 1

Given :

P1 (Power for first lamp) = 40 W

P2 (Power for second lamp) = 100 W

V (Potential difference) = 220 V

Find :

a) Draw a circuit diagram to show the connections.

b) Calculate the current drawn from the electric supply.

c) Calculate the total energy consumed by the two lamps together when the system operate for one hour.

Solution :

a) Refer the attachment.

b) P1 = 40 W, P2 = 100 W and V = 100 V

When Potential difference is same, then

P = V²/R

R = V²/P

Substitute the known values in above formula

R1 = (220)²/40

R1 = 48400/40 ohm ____ (eq 1)

Similarly,

R2 = (220)²/100

R2 = 48400/100 ohm ____ (eq 2)

As, the lamps are connected in parallel then,

1/R = 1/R1 + 1/R2

Substitute the known values in above formula

1/R = 40/48400 + 100/48400

1/R = 4/4840 + 10/4840

1/R = 14/4840

R = 4840/14

R = 345.71 ohm

Now,

I = V/R

I = 220/345.71

I = 0.636 A

I = 0.6 A (approx.)

∴ Current drwan from electric supply is 0.6 A.

c) E = P1 × 1 hr. + P2 × 1 hr.

E = (P1 + P2) × 1 hr.

E = (40 W + 100 W) × 1 hr.

E = 140 W hr.

E = 140/1000 KWhr.

E = 0.14 KWhr.

∴ Energy consumed by two lamps together when they operate for one hour is 0.14 KWhr.

Answer 2

Answer:

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REFERS to ATTACHMENT!!!