2009
1. A fully charged mobile phone with a 12 volts battery is good for a 10 min talk time.
Assume that, during the talk time, the battery delivers a constant current of 2 Amp and its voltage drops linearly from 12 volts to 10 volts as shown in the figure. How much energy does the battery deliver during this talk-time?
a) 220 J
b) 12 kJ
c) 13.2 kJ
d) 14.4 kJ
Solution:
https://www.youtube.com/watch?v=GV1gFYMN_wc
2. In the interconnection of ideal sources shown in figure, it is known that the 60 volts source is absorbing power. Which of the following can be the value of the current source I?
a) 10 A
b) 13 A
c) 15 A
d) 18 A
Solution:
https://www.youtube.com/watch?v=2mwLjmGEWzo
3. An AC source of RMS voltage 20 volts with internal impedance Zi = (1+2j) Ω feeds a load of impedance ZL = (7+4j) Ω in the figure below. The reactive power consumed by the load is
a) 8 VAR
b) 16 VAR
c) 28 VAR
d) 32 VAR
Solution:
https://www.youtube.com/watch?v=w36Rox8j0KA
4. The switch in the circuit shown was on position 'a' for a long time, and is moved to position 'b' at time t=0. The current i(t) for t > 0 is given by
Solution:
https://www.youtube.com/watch?v=ptI9Yzy17OQ
5. In the circuit shown, what value of RL maximizes the power delivered to RL?
a) 2.4 Ω
b) 8/3 Ω
c) 4 Ω
d) 6 Ω
Solution:
https://www.youtube.com/watch?v=yqt0czRs6_I
6. The time domain behaviour of an RL circuit is represented as shown below. For an initial current of i(0) = Vo/R, the steady state value of the current is given by
Solution:
https://www.youtube.com/watch?v=VBFOXuUEuKE
1. A fully charged mobile phone with a 12 volts battery is good for a 10 min talk time.
Assume that, during the talk time, the battery delivers a constant current of 2 Amp and its voltage drops linearly from 12 volts to 10 volts as shown in the figure. How much energy does the battery deliver during this talk-time?
a) 220 J
b) 12 kJ
c) 13.2 kJ
d) 14.4 kJ
2. In the interconnection of ideal sources shown in figure, it is known that the 60 volts source is absorbing power. Which of the following can be the value of the current source I?
a) 10 A
b) 13 A
c) 15 A
d) 18 A
3. An AC source of RMS voltage 20 volts with internal impedance Zi = (1+2j) Ω feeds a load of impedance ZL = (7+4j) Ω in the figure below. The reactive power consumed by the load is
a) 8 VAR
b) 16 VAR
c) 28 VAR
d) 32 VAR
4. The switch in the circuit shown was on position 'a' for a long time, and is moved to position 'b' at time t=0. The current i(t) for t > 0 is given by
5. In the circuit shown, what value of RL maximizes the power delivered to RL?
a) 2.4 Ω
b) 8/3 Ω
c) 4 Ω
d) 6 Ω
6. The time domain behaviour of an RL circuit is represented as shown below. For an initial current of i(0) = Vo/R, the steady state value of the current is given by
great
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