Physics 1B Final Practice
1.) Three particles are shot from the left into a region that contains a uniform
electric field. One particle has a charge of 3Q one has a charge of –3Q and one is
neutral. Determine which path each particle takes.
E-field
2.) Four charges are aligned as below. Determine (a) the magnitude and direction
of the electric field at point P, and (b) the magnitude of the electric potential at
point P. Each side of square is 2 m long. (1.8 × 104V/m, 3.8 × 104 V)
P
3.) At what distance from a 1.0 C charge is the electric potential equal to 12 V?
(7.5 × 108 m)
4.) Determine the E-field and electric potential at the point P. What direction
will the E-field point at point P? What is the change in potential energy of an
atom that moves form point P to point Q? (9.55 × 10 3 V/m, 2.7 × 104 V) Assume
each side is 2.0 m.
Q
5.) In this new arrangement which statements are true?(a)
P
2m
(a)
(b)
(c)
(d)
(e)
2m
The E-field at P is zero, but the electric potential remains unchanged at point P.
Both the E-field and electric potential are zero at P.
The E-field at P is unchanged, but the electric potential will be zero at point P
The E-field at P is unchanged, but the electric potential will decrease at point P
Both the E-field and electric potential will change, and will be non-zero.
6.) At which points is the electric field zero on this line (if it even is anywhere).
(to the right)
+4q
-2q
7.) A charge of 3 µC is placed in a uniform Electric field of strength 34 N/C.
What is the magnitude of the force on this particle? (1 × 10-4 N)
8.) A completely ionized beryllium atom (net charge = +4e)is accelerated through
a potential difference of 6.0 V. What is the increase of KE for the atom? (24 eV)
9.) Two charges of opposite sign are arranged as below, where Q = 2.0 C. How
much work is required to move a 1.0 C charge from infinity to the point P? (9 ×
109 J)
10.) A capacitor has a very large capacitance of 10 F. The capacitor is charged by
placing a potential difference of 2 V between the plates. How many electrons are
on each side of the capacitor? (1.25 × 1020)
11.) The plates of a parallel plate capacitor each have an area of 0.40 m2 and are
separated by a distance of 0.02 m with no material between them. They are
charged until the potential difference between the plates is 3000 V. The charged
capacitor is then isolated. Determine the value of the capacitance. (1.8 × 10-10 F)
12.) How many electrons flow through a battery that delivers a current of 3.0 A
for 12 s?(2.25 × 1020)
13.) Below are values of emf for a battery and current drawn from the battery for
5 circuits. Which circuit has the largest equivalent resistance? Which uses the
most power? (e, d)
(a) emf = 2 V
I = 10 A
(b) emf = 8 V
I = 40A
(c) emf = 10 V
I = 10 A
(d) emf = 15 V
I = 75 A
(e) emf = 20 V
I=5A
14.) A 5 A current is maintained in a simple circuit that consists of a resistor
between the terminals of an ideal battery. If the battery supplies energy at a rate
of 20 W, how large is the resistance? (0.8 Ω)
15.) Two wires A and B and a variable resistor, R, are connected in series to a
battery. Which one of the following results will occur if the resistance R is
increased? (e)
(a) The current through A and B will increase
(b) The voltage across A and B will increase
(c) The voltage across the entire circuit will increase
(d) The power used by the entire circuit will increase
(e) The current through the entire circuit will decrease
16.) Find the equivalent resistance of this circuit. Find the current through R1 and
R2. (82.22 ohms, 0.49 A, 0.22 A)
16.) Find the three currents. E1 = 15 V, E2 = 10 V, R1 = 10 Ω, R2 = 20 Ω, R3 = 15
Ω . (I1 = 0,5 A, I2 = 0.5 A, I3 = 0A)
17.) A charged particle is is fired from a gunwith a velocity of 5.3 × 104 m/s at an
angle of 35° with respect to a 0.0045 T B-field. If the B-field exerts a force of
0.0026 N on the particle determine the magnitude of the charge. (19 µC)
18.) An electron enters a region that contains a magnetic field directed into the
page as shown. The velocity vector of the electron makes angle of 30° with the yaxis. What is the direction of the magnetic force on the electron when it enters
the field? (b)
(a)
(b)
(c)
(d)
(e)
up, out of the page
at angle of 30° below the positive x-axis
at angle of 30° above the positive x-axis
at angle of 60° below the positive x-axis
at angle of 60° above the positive x-axis
19.) A 0.150 m wire oriented horizontally between the poles of an electromagnet
carries a direct current of 12.5 A. The angle between the direction of the current
and that of the magnetic field is 25 °. If the magnetic field strength is 0.625 T,
what is the magnitude and direction of the magnetic field on the wire? (.495 N,
out of the page)
20.) A circular coil consists of 5 loops each of diameter 1.0 m. The coil is placed
in an external B-field of .5 T. When the coil carries a current of 4.0 A, a torque of
magnitude 3.93 N-m acts on it. Determine the angle between the normal to the
plane of the coil and the direction of the B-field. (30 degrees)
21.) An overhead electric power line carries a maximum current of 125 A. What
is the magnitude of the maximum B-field at a point of 4.50 m directly below the
power line? (5.56 × 10-6 T)
22.) A circular loop has a radius of 0.3 m. A B-field is directed perpendicular to
the loop. The B-field goes from 5 T to 10 T in 20 s. What is the induced emf?
What direction will the induced current go? (7 × 10-2 V, CW)
23.) A long, straight wire is in the same plane as a conducting loop. The wire
carries a current as shown in the picture. What direction will the induced current
go, if the loop moves towards and away from the wire. (CCW, CW)
I