Flenst Ted each question carefully and good luckl 1. In the circuit in figure 1,
ID: 1477780 • Letter: F
Question
Explanation / Answer
part a:
when the switch is closed suddenly, the capacitor behaves like a short circui initially.
hence R2 and R3 are connected in parallel.
equivalent resistance=R2*R3/(R2+R3)=2.02*2.02/(2.02+2.02)=1.01 Mega ohms
it is in series with R1.
hence net resistance=R1+1.01=2.02+1.01=3.03 mega ohms
as given that emf is 4.1 kV=4100 volts
voltage E=current*total resistance
==>current=voltage/total resistance=4100/(3.03*10^6)=1.353 mA
current in parallel combination of R2 and R3 is same as current in R1=1.353 mA
as both R2 and R3 are same, current will be divided equally between them
hence current in R2=current in R3=1.353/2=0.6765 mA
part b:
potential difference across R1=current through R1*resistance of R1
=1.353*0.001*2.02*10^6=2733.06 volts
part c:
at t=infinity, the capacitor is saturated and become open circuit
hence there is no current through R3.
i3=0
now R2 and R1 in series.
net resistance in the circuit=2.02+2.02=4.04 mega ohms
then current=emf/resistance
=4100/(4.04*10^6)=1.01485 mA
hence i1=i2=1.01485 mA
part d:
potential difference across R1=current through R1*resistance of R1
=i1*2.02*10^6
=2049.997 volts=2050 volts
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