Q 67

Kirchhoff's loop rule is a statement of
A)the law of conservation of momentum.
B)the law of conservation of charge.
C)the law of conservation of energy.
D)the law of conservation of angular momentum.
E)Newton's second law.

Q 68

A resistor,an uncharged capacitor,a dc voltage source,and an open switch are all connected in series.The switch is closed at time t = 0 s.Which one of the following is a correct statement about this circuit?
A)The charge on the capacitor after four time constants is about 98% of the maximum value.
B)The charge on the capacitor after one time constant is 50% of its maximum value.
C)The charge on the capacitor after one time constant is 1/e of its maximum value.
D)The voltage on the capacitor after one time constant is 1/e of the maximum value.
E)The voltage on this capacitor after one time constant is 100% of its maximum value.

Q 69

A capacitor C is connected in series with a resistor R across a battery and an open switch.If a second capacitor of capacitance 2C is connected in parallel with the first one,the time constant of the new RC circuit will be
A)the same as before.
B)twice as large as before.
C)three times a large as before.
D)one-half as large as before.
E)one-fourth as large as before.