Homework Assignment 2
Due Sept. 4, 1998

1. 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.
   

2. Problem 1-10 from the text:
   The current through a device is given by i(t) = 0.05t A. How many coulombs enter the device between time t = 0 s and t = 5 s?

3. 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,
   1. Determine the device power when it operates at point A and state whether the device is absorbing or delivering power.
   2. Repeat part (a) when the device operates at points B and C.
   3. 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.
   

4. 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) = -5e^-100t mA.
   1. Find the power delivered by the device at t = 0, t = 5 ms and t = 25 ms.
   2. Find the total energy delivered by the device during the interval .

5. 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.)

6. 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
   1. A linear 10-k resistor with v = 12V.
   2. An ideal 10-mA current source with the arrow directed upward and p = 20 mW.
   3. An ideal 15-V voltage source with the plus terminal at the top and i = -8 mA.
   4. An ideal switch with i = -20mA.
   

7. 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).

8. Problem 2-11 from the text:
   For the circuit in Figure P2-11,
   1. Identify the nodes and at least two loops.
   2. Identify any elements connected in series or in parallel.
   3. Write KCL and KVL connection equations for the circuit.
   4. If i₁ = 6 mA and i₂ -4 mA, find the other element currents.
   

9. Problem 2-15 from the text:
   The circuit in Figure P2-15 is organized around the three signal lines A, B, and C.
   1. Identify the nodes and at least three loops in the circuit.
   2. Write KCL connection equations for the circuit.
   3. If i₃ = 15 mA, i₄ = -12 mA, and i₅ = 5 mA, find the other element currents.
   

10. 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.