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Electricity Review
SWHS AP Physics Year 1
Multiple Choice:
1.
Name:
An isolated pair of charged particles X and Y, with masses mX and mY = 2mX , repel one another. The
electrostatic force is the only force between them. If particle X accelerates at 2.2 m/s2, what is the
acceleration of particle Y?
(A) 0 m/s2
(B) 0.55 m/s2
(C) 1.1 m/s2
(D) 2.2 m/s2
(E) 4.4 m/s2
Questions 2-3:
In the circuit above, the resistors all have the same resistance. The battery, wires, and ammeter have
negligible resistance. A closed switch also has negligible resistance.
2.
Closing which of the switches will produce the greatest power dissipation in R2?
(A) S1 only
(B) S2 only
(C) S1 and S2 only
(D) S1 and S3 only
(E) S1, S2, and S3
3.
Closing which of the switches will produce the greatest reading on the ammeter?
(A) S1 only
(B) S2 only
(C) S3 only
(D) S1 and S2 only
(E) S1 and S3 only
4.
The circuit shown above left is made up of a variable resistor and a battery with negligible internal
resistance. A graph of the power P dissipated in the resistor as a function of the current I supplied by
the battery is given above right. What is the emf of the battery?
(A) 0.025 V
(B) 2.5 V
(C) 6.25 V
(D) 40 V
5.
The total equivalent resistance between points X and Y in the circuit shown above is
(A) 3 Ω
(B) 4 Ω
(C) 5 Ω
(D) 6 Ω
6.
The four resistors below have the lengths and cross sectional areas indicated and are made of
material with the same resistivity. Which has the least resistance?
(A)
7.
(B)
In the diagrams above, resistors R1 and R2 are shown in two different connections to the same
source of emf E that has no internal resistance. How does the power dissipated by the resistors in
these two cases compare?
(A) It is greater for the series connection.
(B) It is greater for the parallel connection.
(C) It is different for each combination, but one must know the values of R1 and R2 to know which is
greater.
(D) It is different for each combination, but one must know the values of E to know which is greater.
8.
Two concentric circular loops of radii b and 2b, made of the same type of wire, lie in the plane of the
page, as shown above. The total resistance of the wire loop of radius b is R. What is the resistance of
the wire loop of radius 2b?
(A) R/4
(B) R/2
(C) 2R
(D) 4R
Questions 9-10:
Five identical light bulbs, each with a resistance of 10 Ω, are connected in a simple electrical circuit with a
switch and a 10 V battery as shown in the diagram below.
9.
The steady current in the above circuit would be closest to which of the following values?
(A) 0.2 amp
(B) 0.37 amp
(C) 0.5 amp
(D) 2.0 amp
10.
Which bulb (or bulbs) could burn out without causing other bulbs in the circuit to also go out?
(A) only bulb D
(B) only bulbs C or D
(C) only bulb E
(D) only bulbs A or E
11.
The circuit shown above contains two resistors of resistance R and 2R. The graph shows the total
energy E dissipated by the smaller resistor as a function of time. Which of the following shows the
corresponding graph for the larger resistor?
(A)
(B)
(C)
(D)
12.
When a negative charged rod is brought near, but does not touch, the initially uncharged
electroscope shown above, the leaves spring apart (I). When the electroscope is then touched with a
finger, the leaves collapse (II). When next the finger and finally the rod are removed, the leaves
spring apart a second time (III). The charge on the leaves is
(A) positive in both I and III
(B) negative in both I and III
(C) positive in I, negative in III
(D) negative in I, positive in III
13.
Two positive point charges repel each other with force 0.36 N when their separation is 1.5 m. What
force do they exert on each other when their separation is 1.0 m?
(A) 0.81 N
(B) 0.36 N
(C) 0.24 N
(D) 0.16 N
14.
Two point objects each carrying charge 10Q are separated by a distance d. The force between them
is F. If half the charge on one object is transferred to the other object while at the same time the
distance between them is doubled, what is the new force between the two objects?
(A) 0.19 F
(B) 0.25 F
(C) 4.0 F
(D) no change in F
15.
Sphere X of mass M and charge +q hangs from a string as shown above. Sphere Y has an equal
charge +q and is fixed in place at a distance d directly below sphere X. If sphere X is in equilibrium,
the tension in the string is most nearly
(A) Mg
(B) Mg-kq/d
(C) Mg + kq2/d2
(D) Mg – kq2/d2
Free Response:
1.
A battery with an emf of 24 V and an internal resistance of 1 ohm is connected to an external
circuit as shown above. Determine each of the following:
(a) The equivalent resistance of the combination of the 4 Ω, 8 Ω and 12 Ω resistors.
(b) The current in the 5 Ω resistor
(c)
The terminal voltage, VAC of the battery
(d) The rate at which energy is dissipated in the 12 Ω resistor
(e) The magnitude of the potential difference VBC
2.
The circuit above contains a battery with negligible internal resistance, a closed switch S,
and three resistors, each with a resistance of R or 2R.
(a) Rank the currents in the three resistors from greatest to least, with number 1 being
greatest. If two resistors have the same current, give them the same ranking.
______ IA
______ IB
______ IC
Justify your answer.
(b) Rank the voltages in the three resistors from greatest to least, with number 1 being
greatest. If two resistors have the same voltage, give them the same ranking.
______ VA
Justify your answer.
______ VB
______ VC
For parts (c) through (d), use Emf = 12 V and R = 200 Ω.
(c)
Calculate the equivalent resistance of the circuit.
(d) Calculate the current in resistor RC.
3.
Two point charges are fixed on the y-axis at the locations shown in the figure above. A
charge of +q is located at y = +a and a charge of +2q is located at y = -a. A third charge
of –q is first placed at an arbitrary point A (x = -x0) on the x-axis as shown in the figure
below.
(a) Write expressions in terms of q, a, x0, and fundamental constants for the magnitudes
of the forces on the –q charge at point A caused by each of the following.
i. The +q charge
ii. The +2q charge
(b) The –q charge can also be placed at other points on the x-axis. At each of the labeled
points (A, B, and C) in the following diagram, draw a vector to represent the direction
of the net force on the –q charge due to the other two charges when it is at those
points.