A 15 V source is connected across a 12 Ω resistor. How much energy is used in three minutes?
A. 938 Wh
B. 0.938 Wh
C. 56.25 Wh
D. 5.6 Wh
Answer: Option B
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v=IR
I=V/R
=15V/12ohm
=1.25A.
P=VI
=15V * 1.25A
= 18.5W.
Energy = Power * time
=18.75W * 0.05h
=0.938 Wh.
v=15
r=12
i=v/r
i=15/12=1.25A
p=vi=15x1.25=18.75w
E=18.57x(3/60)=0.938
E = P×t (P= V^2/R,)
{ (t=3min=3/60h).= 0.05h }
E = V^2/R × t ,. E= (15)^2/12 × 0.05
E = 225/12 × 0.05 , = 18.75×0.05
E = 0.938wh
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