1.
A certain sample carries a current of 4 A when the potential difference is 2 V and a current of 10 A when the potential difference is 4 V. This sample:
A.
obeys Ohm's law
B.
has a resistance of 0.5 Ω at 2 V
C.
has a resistance of 2.5 Ω at 2 V
D.
has a resistance of 25 Ω at 2 V
E.
does not have a resistance


2.
A circular loop of wire is positioned half in and half out of a square region of constant uniform magnetic field directed into the page, as shown. To induce a clockwise current in this loop:
A.
move it in +x direction
B.
move it in +y direction
C.
move it in –y direction
D.
move it in –x direction
E.
increase the strength of the magnetic field


3.
A 3-Ω and a 1.5-Ω resistor are wired in parallel and the combination is wired in series to a 4-Ω resistor and a 10-V emf device. The current in the 3-Ω resistor is:
A.
0.33 A
B.
0.67 A
C.
2.0 A
D.
3.3 A
E.
6.7 A


4.
In the diagrams, all light bulbs are identical and all emf devices are identical. In which circuit (I, II, III, IV, V) will the bulbs be dimmest?
A.
I
B.
II
C.
III
D.
IV
E.
V


5.
Five cylindrical wires are made of the same material. Their lengths and radii are
 
wire 1: length E , radius r
 
wire 2: lenth 3E /2, radius r/2
 
wire 3: length E /2, radius r/2
 
wire 4: length E , radius r/2
 
wire 5: length 5E , radius r/2
Rank the wires according to their resistances, least to greatest.
A.
1, 2, 3, 4, 5
B.
5, 4, 3, 2, 1
C.
1 and 2 tie, then 5, 3, 4
D.
1, 3, 4, 2, 5
E.
1, 2, 4, 3, 5


6.
When switch S is open, the ammeter in the circuit shown reads 2.0 A. When S is closed, the ammeter reading:
A.
increases slightly
B.
remains the same
C.
decreases slightly
D.
doubles
E.
halves


7.
A magnet moves inside a coil. Consider the following factors:
 
I.
 
strength of the magnet
 
II.
 
number of turns in the coil
 
III.
 
speed at which the magnet moves
Which can affect the emf induced in the coil?
A.
I only
B.
II only
C.
III only
D.
I and II only
E.
I, II, III


8.
In Ampere's law, A4d´ = μ0i, the integration must be over any:
A.
surface
B.
closed surface
C.
path
D.
closed path
E.
closed path that surrounds all the current producing 4


9.
A uniform magnetic field is directed into the page. A charged particle, moving in the plane of the page, follows a clockwise spiral of decreasing radius as shown. A reasonable explanation is:
A.
the charge is positive and slowing down
B.
the charge is negative and slowing down
C.
the charge is positive and speeding up
D.
the charge is negative and speeding up
E.
none of the above


10.
The diagrams show three circuits with identical batteries, identical inductors, and identical resistors. Rank them according to the current through the battery just after the switch is closed, from least to greatest.
A.
3, 2, 1
B.
2 and 3 ties, then 1
C.
1, 3, 2
D.
1, 2, 3
E.
3, 1, 2


11.
The equivalent resistance between points 1 and 2 of the circuit shown is:
A.
3 Ω
B.
4 Ω
C.
5 Ω
D.
6 Ω
E.
none of the above Ω


12.
A portion of a circuit is shown, with the values of the currents given for some branches. What is the direction and value of the current i?
A.
↓, 6A
B.
↑, 6A
C.
↓, 4A
D.
↑, 4A
E.
↓, 2A


13.
Four circuits have the form shown in the diagram. The capacitor is initially uncharged and the switch S is open.

The values of the emf 5, resistance R, and the capacitance C for each of the circuits are
 
circuit 1: 5 = 18 V, R = 3 Ω, C = 1 μF
 
circuit 2: 5 = 18 V, R = 6 Ω, C = 9 μF
 
circuit 3: 5 = 12 V, R = 1 Ω, C = 7 μF
 
circuit 4: 5 = 10 V, R = 5 Ω, C = 7 μF
Rank the circuits according to the time after switch S is closed for the capacitors to reach half their final charges, least to greatest.
A.
1, 2, 3, 4
B.
4, 3, 2, 1
C.
1, 3, 4, 2
D.
4, 2, 1, 3
E.
3, 1, 2, 4


14.
Two wires made of different materials have the same uniform current density. They carry the same current only if:
A.
their lengths are the same
B.
their cross-sectional areas are the same
C.
both their lengths and cross-sectional areas are the same
D.
the potential differences across them are the same
E.
the electric fields in them are the same


15.
A magnetic field CANNOT:
A.
exert a force on a charge
B.
accelerate a charge
C.
change the momentum of a charge
D.
change the kinetic energy of a charge
E.
exist


16.
The diagram shows a straight wire carrying current i in a uniform magnetic field. The magnetic force on the wire is indicated by an arrow but the magnetic field is not shown. Of the following possibilities, the direction of the magnetic field is:
A.
to the right
B.
opposite the direction of ¢
C.
in the direction of ¢
D.
into the page
E.
out of the page


17.
The diagrams show five possible orientations of a magnetic dipole ± in a uniform magnetic field 4. For which of these does the magnetic torque on the dipole have the greatest magnitude?
A.
I
B.
II
C.
III
D.
IV
E.
V


18.
At any point the magnetic field lines are in the direction of:
A.
the magnetic force on a moving positive charge
B.
the magnetic force on a moving negative charge
C.
the velocity of a moving positive charge
D.
the velocity of a moving negative charge
E.
none of the above


19.
The diagram shows three equally spaced wires that are perpendicular to the page. The currents are all equal, two being out of the page and one being into the page. Rank the wires according to the magnitudes of the magnetic forces on them, from least to greatest.
A.
1, 2, 3
B.
2, 1 and 3 tie
C.
2 and 3 tie, then 1
D.
1 and 3 tie, then 2
E.
3, 2, 1


20.
Two long parallel straight wires carry equal currents in opposite directions. At a point midway between the wires, the magnetic field they produce is:
A.
zero
B.
non-zero and along a line connecting the wires
C.
non-zero and parallel to the wires
D.
non-zero and perpendicular to the plane of the two wires
E.
none of the above


21.
A beam of electrons is sent horizontally down the axis of a tube to strike a fluorescent screen at the end of the tube. On the way, the electrons encounter a magnetic field directed vertically downward. The spot on the screen will therefore be deflected:
A.
upward
B.
downward
C.
to the right as seen from the electron source
D.
to the left as seen from the electron source
E.
not at all


22.
A student kept her 60 watt 120 volt study lamp turned on from 2 PM until 2 AM. How many coulombs went through it?
A.
150
B.
3,600
C.
7,200
D.
9,000
E.
none of the above


23.
A current of 0.3 A is passed through a lamp for 2 minutes using a 6 V power supply. The energy dissipated by this lamp during the 2 minutes is:
A.
1.8 J
B.
12 J
C.
20 J
D.
36 J
E.
216 J


24.
The diagrams show three circuits consisting of concentric circular arcs (either half or quarter circles of radii r, 2r, and 3r) and radial lengths. The circuits carry the same current. Rank them according to the magnitudes of the magnetic fields they produce at C, least to greatest.
A.
1, 2, 3
B.
3, 2, 1
C.
1, 3, 2
D.
2, 3, 1
E.
2, 1, 3


25.
Four long straight wires carry equal currents into the page as shown. The magnetic force exerted on wire F is:
A.
north
B.
east
C.
south
D.
west
E.
zero


26.
Solenoid 2 has twice the radius and six times the number of turns per unit length as solenoid 1. The ratio of the magnetic field in the interior of 2 to that in the interior of 1 is:
A.
2
B.
4
C.
6
D.
1
E.
1/3


27.
The diagram shows an inductor that is part of a circuit. The direction of the emf induced in the inductor is indicated. Which of the following is possible?
A.
The current is constant and rightward
B.
The current is constant and leftward
C.
The current is increasing and rightward
D.
The current is increasing and leftward
E.
None of the above


28.
A long straight wire is in the plane of a rectangular conducting loop. The straight wire carries a constant current i, as shown. While the wire is being moved toward the rectangle the current in the rectangle is:
A.
zero
B.
clockwise
C.
counterclockwise
D.
clockwise in the left side and counterclockwise in the right side
E.
counterclockwise in the left side and clockwise in the right side


29.
You wish to triple the rate of energy dissipation in a heating device. To do this you could triple:
A.
the potential difference keeping the resistance the same
B.
the current keeping the resistance the same
C.
the resistance keeping the potential difference the same
D.
the resistance keeping the current the same
E.
both the potential difference and current


30.
A copper penny slides on a horizontal frictionless table. There is a square region of constant uniform magnetic field perpendicular to the table, as shown. Which graph correctly shows the speed v of the penny as a function of time t?
A.
I
B.
II
C.
III
D.
IV
E.
V