**Homework Assignment 2 **

Due Sept. 4, 1998

- Problem 1-8 from the text:

Figure P1-8 shows a plot of the net positive charge flowing in a wire versus time. Sketch the corresponding current during the same time period.

- Problem 1-10 from the text:

The current through a device is given by*i(t)*= 0.05*t*A. How many coulombs enter the device between time*t*= 0 s and*t*= 5 s? - Problem 1-17 from the text (but use figure below):

A two-terminal device has the current versus voltage characteristics shown below. Assuming the passive sign convention,- Determine the device power when it operates at point A and state whether the device is absorbing or delivering power.
- Repeat part (a) when the device operates at points B and C.
- Identify the operating point on the curve (it could be a point other than A, B, or C) at which the device delivers the most power.

- Problem 1-24 from the text:

The voltage across and current through a two-terminal device are*v(t)*= 5*e*^{-100t}V and*i(t)*= -5*e*^{-100t}mA.- Find the power delivered by the device at
*t*= 0,*t*= 5 ms and*t*= 25 ms. - Find the total energy delivered by the device during the interval .

- Find the power delivered by the device at
- Problem 1-26 from the text:

In complete darkness the voltage across and current through a two-terminal light detector are +5.6 V and +8 nA. In full sunlight the voltage and current are +0.9 V and +4 mA. Express the light/dark power ratio of the device in decibels (dB). (See Problem 1-6 for the definition of a decibel.) - Problem 2-1 from the text:

Figure P2-1 shows a general two-terminal element with voltage and current reference marks assigned. Find the unknown electrical variables when the element is- A linear 10-k resistor with
*v*= 12V. - An ideal 10-mA current source with the arrow directed upward and
*p*= 20 mW. - An ideal 15-V voltage source with the plus terminal at the top and
*i*= -8 mA. - An ideal switch with
*i*= -20mA.

- A linear 10-k resistor with
- Problem 2-10 from the text:

A fuse contains a metal link that melts to create an open circuit when the current through the device exceeds*I*_{BLOW}. When the current is less the*I*_{BLOW}, the fuse acts like a fixed resistor*R*_{FUSE}. For a certain fuse,*I*_{BLOW}= 20 mA and*R*_{FUSE}= 10. Sketch the current through the fuse versus time when the voltage across the fuse increases linearly with time (i.e.,*v*=*t*). - Problem 2-11 from the text:

For the circuit in Figure P2-11,- Identify the nodes and at least two loops.
- Identify any elements connected in series or in parallel.
- Write KCL and KVL connection equations for the circuit.
- If
*i*_{1}= 6 mA and*i*_{2}-4 mA, find the other element currents.

- Problem 2-15 from the text:

The circuit in Figure P2-15 is organized around the three signal lines A, B, and C.- Identify the nodes and at least three loops in the circuit.
- Write KCL connection equations for the circuit.
- If
*i*_{3}= 15 mA,*i*_{4}= -12 mA, and*i*_{5}= 5 mA, find the other element currents.

- Problem 2-17 from the text:

The circuit in Figure P2-17 is called a multitap voltage divider. Use KCL to find the output voltage when the switch is in position A, B, C, D, and E.*Hint:*The output voltage is defined relative to ground.