Name:
ID: A
Student Number:
Physics 2140: Hour Exam 2
Wednesday, June 13,2007
Each Question is worth 10 points
Please show your work in solving ~hefollowingproblems.No credit will be awardedfor answers without evidence of
work supporting the answer.
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1 . How much current is flowing in one of the 1 0 - 0 resistors?
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2. A 10-V-emf battery is connected in series with the following: a 2-pF capacitor, a 2-R resistor, an ammeter, and
a switch, initially open; a voltmeter is connected in parallel across the capacitor. After the switch has been
closed for a relatively long period (several seconds, say), what are the current and capacitor voltage readings,
respectively?
Name:
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ID: A
3. A proton is released such that it has an initial speed of 4.0 x 1 O5 m/s from left to right across the page. A
magnetic field of 1.2 T is present at an angle of 30" to the horizontal direction (or positive x axis). What is the
magnitude of the force experienced by the proton? (q, = 1.6 x 1 0-l9 C)
4. A proton moves across the Earth's equator in a northeasterly direction. At this point the Earth's magnetic field
has a direction due north and is parallel to the surface. What is the direction of the force acting on the proton
at this instant?
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5. A solenoid with 500 turns, 0.1 0 m long, carrying a current of 4.0 A and with a radius of 1 0-2 m will have what
strength magnetic field at its center? (magnetic permeability in empty space po = 4 n x 1 0-7 T.m/A)
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Name:
ID: A
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A flat coil of wire consisting of 20 turns, each with an area of 50 cm2, is positioned perpendicularly to a
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6.
uniform magnetic field that increases its magnitude at a constant rate from 2.0 T to 6.0 T in 2.0 s. If the coil
has a total resistance of 0.40 R, what is the magnitude of the induced current?
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7. A large jetliner with a wingspan of 40 m flies horizontally and due north at a speed of 300 m/s in a region where
the magnetic field of the earth is 60 pT directed 50" below the horizontal. What is the magnitude of the
induced emf between the ends of the wing?
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8. A motor with a coil resistance of 10 R is attached to a voltage supply of 90 V. What is the current in the motor
when it is running at its maximum speed with a back emf of 60 V?
Name:
ID: A
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9. An emf of 0.32 V is induced in a 0.40-H inductor. What is the rate of change of current through the inductor?
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10. A hair dryer draws 1 200 W, a curling iron draws 800 W, and an electric light fixture draws 500 W. If all three
of these appliances are operating in parallel on a 120-V circuit, what is the total current drawn?
1 1. Resistors of values 6.OR, 4.OR, 10.0R and 7.0Q are combined as shown. What is the equivalent resistance for
this combination?
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Name:
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ID: A
12. When a 2 4 . 0 4 resistor is connected across a 12.0-V battery, a current of 482 mA flows. What is the resulting
terminal voltage
- of the battery?
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13. A 100-m-long wire carrying a current of 4.0 A will be accompanied by a magnetic field of what strength at a
distance of 0.050 m from the wire? (magnetic permeability in empty space po = 4 n x lo-' T.m/A)