Physics 1402 Practice Problems for Exam II
1. A metal wire has a resistance of 10.0 ohms at a temperature of 20 degrees C. If
the same wire has a resistance of 10.55 ohms at 90 degrees C, what is the
resistance of the wire when its temperature is -20 degrees C?
a. 0.7 ohms
b. 9.69 ohms
c. 10.31 ohms
d. 13.8 ohms
e. 70 ohms
2. A steam turbine at an electric power plant delivers 4500 kW of power to an
electrical generator which converts 95% of this mechanical energy into electrical
energy. What is the current delivered by the generator if it delivers at 36000 V?
a. 660 A
b. 1000 A
c. 1190 A
d. 5900 A
3. Three resistors connected in parallel have individual values of 4.o ohms, 6 ohms,
and 10 ohms. If this combination is connected to a 12 V battery, what is the
current in the 10 ohm resistor?
a. .55 A
b. 5.2 A
c. 1.2 A
d. 2.0 A
4. The following three appliances are connected to a 120 volt house circuit: (i) a
toaster, 1200, (ii) a coffee pot, 750 Watt, (iii) a microwave, 600 Watt. If all
operate at the same time, what total current would they draw?
a. 3 A
b. 5 A
c. 10 A
d. 21 A
5. A solenoid with 500 turns, 0.10 mm long, carrying a current of 4.0 A and with a
radius of .01m will have what strength magnetic field at its center? (magnetic
permeability in empty space µ = 4π X 10-7 T - m/A).
a. 31 X 10-4 T
b. 62 X 10-4 T
c. 125 X 10-4 T
d. 250 X 10-4 T
6. An electron which moves with a speed of 30,000 m/s perpendicular to a uniform
magnetic field of 0.40 T experiences a force of what magnitude?
a. 4.8 X10-14 T
b. 19.2 X 10-16 T
c. 22 X 10-24 T
d. zero
7. An AC series circuit of 20 ohms resistor, a capacitor of 0.75 microfarad and an
inductor of 120 mH. What frequency should be used to create a resonance
condition in the circuit?
a. 159 Hz
b. 318 Hz
c. 637 Hz
d. 530 Hz
8. A proton moves with a uniform velocity of 8 X 106 m/s along the X-axis. It enters
a region where a magnetic field of magnitude 2.5 T, is directed at an angle of 600
to the X-axis and lying in the X-Y plane as shown on the diagram. (q for the
proton is 1.6 X 10-19 C)
(a) Calculate the initial force on the
proton (3 pts)
(b) Use the right hand rule to find the direction of the force (2 pts)