Ch 18,19,20 Rehearsal Test
1. Electric field lines cross each other at
(a) 1800
(b) 00
(c) 900
(d) they never cross each other
2. A 6 C charge experiences a force of 240 N in an electric field of strength ________
(a)
(b)
(c)
(d)
1440 N/C
40 N/C
1.44 x 10-6 N/C
4 x 107 N/C
3. Two isolated metal spheres A and B charged to + 17 C and – 3 C respectively, are
touched and separated. The charge on each sphere is
(a)
(b)
(c)
(d)
(e)
17 C
14 C
3 C
7 C
-7 C
4. A hollow metal sphere of radius 4 m is charged to 12 C. The electric field inside the
sphere at a distance of 2 m from the surface is
(a)
(b)
(c)
(d)
2700 N/C
3 x 10-6 N/C
zero
5400 N/C
5. An insulator of dielectric constant 5.0 is introduced between the plates of a parallel
plate capacitor of capacitance 6 F. The capacitance then
(a) increases to 30 F
(b) decreases to 1.2 F
(c) remains the same
6. In a series circuit
(a) current thru the circuit remains constant
(b) voltage drops across the devices remain constant
(c) both voltage and current remain constant
(d) none of the above
7. In a parallel circuit, the total resistance of the circuit __________ when more devices
are added .
(a) increases
(b) decreases
(c) remains constant
8. In a parallel circuit if one bulb burns out the other devices in parallel branches
(a) also burn out
(b) burn more brightly
(c) burn less brightly
(d) burn as bright as before
9. In a parallel circuit, as compared to a thick filament the current in a thin filament is
_________ because the resistance of the thin filament is __________.
a) greater
b) smaller
c) the same
10. In a series circuit, as compared to a thick filament the voltage across a thin filament
is _________ because the resistance of the thick filament is __________, whereas
the current thru both the filaments is ____________.
a) greater
b) smaller
c) the same
11. An ammeter is always placed in _____________, whereas an Voltmeter is placed in
______________ in a circuit. This ___________ on the type of circuit.
(a) parallel
(b) series
(c) depends
(d) does not depend
12. In a series circuit if you add more bulbs, the current in the circuit
(a) increases
(b) decreases
(c) remains the same
13. A hair dryer with a power rating of 2000 W, operating at 100 V draws a current of
(a) 0.05 A
(b) 20 A
(c) 2 A
14. Two resistors of 240  and 360  are connected to a 12 V battery in series, the
current through the 240  resistor is
(a)
(b)
(c)
(d)
20 A
0.05 A
0.24 A
0.02 A
15. Two resistors of 12  and 24  are connected in parallel to a 6 V battery, the current
through the 12  resistor is
(a)
(b)
(c)
(d)
0.25 A
0.5 A
0.75 A
4A
1.
A small drop of water is suspended motionless in air by a uniform electric field that
is directed upward and has a magnitude of 8640 N/C. The mass of the water drop is
3.5 x 10--14 kg. (a) Is the water drop positively or negatively charged. (b) How many
excess protons or electrons does it have ?
m = 3.5 x 10-9 kg
E = 8640 N/C
(a) Identify the given and the unknown variable
(b) Identify the equations to be used
(c) Show your work and box your answers
2.
The membrane surrounding a living cell has an area of 5.0 x 10-9 m2 and a thickness
of 1.5 x 10-8 m. Assume that the membrane behaves as a parallel plate capacitor and
has a dielectric constant of 5.0, and the potential difference on the outer surface of
the membrane is 65 mV (0.065 V) greater than the inside surface. (a) How much
charge resides on the outer surface. (b) What is the total electrical potential energy
stored by the membrane.
(a) Identify the given and the unknown variable
(b)Identify the equations to be used
(c) Show your work and box your answers
3.
The circuit in the drawing contains three identical resistors in a series circuit . The
12 V battery delivers 36 W of power to the circuit. (a)What is the total current in the
circuit ? Show the direction and amount of current in the circuit. (b)What is the
resistance of each resistor ? (c) What is the voltage across the first resistance. Show
how you would introduce an ammeter and voltmeter in the circuit below.
R
R
R
12 V
The following shows a parallel circuit with three resistors (R1 = 3 , R2 = 2 , R3 = 1 ,
connected to a 6 V battery. (a) What are i1 i2 and i3. What is the total current provided by
the battery? Show the currents and their direction in the circuit below. (b) What is the
equivalent resistance of the circuit? (c) What are the voltages across the three
resistances equal to?
6V
For full credit, draw the circuit diagrams neatly labeling all the elements (voltages
and resistances) and showing the directions of current flow in the circuit at the
appropriate places.
4. (a) Build a series circuit, with a 54 , 84  and 102  resistances connected to a 12
V battery. What is the total resistance and current in the circuit, and what are the
voltages across the three resistances? What is the sum of the voltage drops across the
resistors equal to?
The total resistance of the circuit R =
The current in the circuit I =
V1 =
V2 =
V3 =
V1 + V2 + V3 = V = ?
(b) Build a parallel circuit with 5 , 3  and 9  resistors connected to a 45 V battery.
What are the currents in the three branches and what are the voltages across the resistors
each equal to. What is the total current from the battery equal to? What is the total
resistance?
The voltage across the circuit V =
I1 =
I2 =
I3 =
I1 + I2 + I3 = I = ?
The total resistance of the circuit R =
Verify if this R is equal to the equivalent resistance in a parallel circuit.