Only full detailed answer will be rated Compared to a 30.0 Ohm resistor another
ID: 2256541 • Letter: O
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Only full detailed answer will be rated
Compared to a 30.0 Ohm resistor another resistor made from the same material has twice (2 00X) the cross sectional area, but half (0 500x) the length. If this second resistor is connected in a series with a 12.0 V battery, what is the current in this circuit? (20.4) In a circuit, a 24.0-V battery is in series with a 4.00-Ohm resistor and an unknown resistor. (All three are in one unbranching current loop.) If there is an 8.00-V drop over the 4.00-Ohm resistor, what is the resistance of the second resistor? (20.7)Explanation / Answer
1) When S1 is opened and S2 is closed, we will have a capacitor discharging from the resistor R2
The bulb will glow for some time and then turn off as the current value decreases from maximum to minimum.
2) V = Vo ( 1 - e^(-t/RC) )
RC = 300 * 0.002 = 0.6 sec
Vo = 15 V
So, voltage across capacitor after t = 5.0 sec = Vo(1 - e^(-5 / 0.6) ) = 14.99 V i.e approx 15 V
Thus, it is almost completely charged.
Now, when S2 is on and S1 is off,
RC = 600 * 0.002 = 1.2 sec
Thus, while discharging,
V = Vo ( e^ (-t/RC) )
Thus at t = 4.0 sec
V = 15 (e^(-4/1.2)) = 0.535 V is the potential difference
Charge = CV = 0.002 * 0.535 = 1.07 * 10^-3 coloums = 1.07mC
3) the third part is a bit ambiguous one. At what instant does it want the switch #1 to be closed.
What is the condition of switch #2 at that time.
considering switch S2 open:
power dissipated = v^2 / R = 15^2 / 300 = 225 / 300 = 0.75W
Please let me know if you have any doubts and I shall try to help you out over here. Hope this helps. Thanks.
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