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Electronics problems involving capacitor, resistor etc.

1) A tungsten filament has a resistance of 3 OMP at 20 degrees. When connected
to a 100V power supply a current of 6.0A passes through a filament. If the
filament is connected to the same power supply when it is at 2000 degrees,
what will be the current through the filament and its power loss?

2) A battery whose emf is 12V is used to operate a device that draws 6.5A. When
the device is operating the battery voltage is checked and found to be 8.2V.
What will be the battery voltage be when it is connected to a device drawing

3) An electric car is designed to run off a bank of 12V batteries with total
energy storage 2*10^7 j. If the electric motor draws 800W in moving the car at
a speed of 20m/s, how far will the car go before it runs out of "juice"?

4) In the following circuit, what is the current through R1 at T=1 second after
the switch is closed? How long does it take the capacitor to be 95% fully

The diagram:
R1 and R2 are parallel to each other. R1=2M* omg R2=6M* omg (M is mega, not
A capacitor is connected in the circuit. C=2uF


Solution Preview

Please see the attached file.

(1)Ans: Tungsten like most other metals has a positive temperature coefficient of resistance of about 4.5 x 10 -3 K-1
It's resistance is given by, R = R0[1 + (T - ...

Solution Summary

More than 300 words solution. Easy to understand explanations for all 4 problems.