Question

a bulb is rated 40 volt 220 volt find the current drawn by it when it is connected to a 220 volt supply also find its resistance if the given bulb is replaced by a bulb of rating 25 Watt 220 volt will there be any change in the value of current and resistance justify your answer in determine the change​

Answer 1

p = 40
v= 220
I= p/v
therefore i= 40/220

=0.182.
r = v /i
r= 1210.

now p = 25
v=220.
i = p/v

i= 0.113

now r = v/1
=1936.


i decreases and r increases.

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Answer 2

Hey dear,

● Answer -
∆I = 0.0682 A
∆R = 727 ohm

● Explanation -
# Given -
P1 = 40 W
P2 = 25 W
V = 220 V


# Formula -
Power of bulb is given by - P = VI
Resistance is calculated by - R = V / I

# Solution -
Initially,
P1 = VI1
40 = 220 × I1
I1 = 0.1818 A

R1 = V / I1
R1 = 220 / 0.1818
R1 = 1210 ohm

Later,
P2 = VI2
25 = 220 × I2
I2 = 0.1136 A

R2 = V / I2
R2 = 220 / 0.1136
R2 = 1937 ohm


Change in current -
∆I = I2 - I1 = 0.1136 - 0.1818 = 0.0682 A

Change in resistance -
∆R = R2 - R1 = 1937 - 1210 = 727 ohm

Hope this helped you...