Transcript Document

St Columba’s high School
Electricity and Electronics
•Electric Fields and Resistors in
Circuits
•Alternating Current and
Voltage
Which of the following statements
is/are correct?
A. There is a force on a charge in an E-field.
B. When an E-field is applied to a conductor, free charges
move through it.
C. Work is done when a charge is moved in an E-field.
ly
A
,B
an
d
on
an
d
C
C
d
0%
C
0%
on
ly
on
B
on
0%
ly
0%
ly
0%
an
A only
B only
A and C only
B and C only
A, B and C
A
1.
2.
3.
4.
5.
30
One Volt is…….
O
ne
C
ne
Jo
ul
e
C
ou
ou
lo
lo
m
O
m
b
ne
b
pe
Jo
rS
ul
e
...
pe
O
rC
ne
ou
Jo
lo
ul
m
e
O
b
pe
ne
r
C
Se
ou
co
lo
nd
m
b
pe
rJ
ou
le
0% 0% 0% 0% 0%
O
1. One Joule Coulomb
2. One Coulomb per
Second
3. One Joule per
Coulomb
4. One Joule per
Second
5. One Coulomb per
Joule
30
Metal parallel plates X and Y are
connected to a 3.0 V d.c. supply as
shown. What is the gain in electrical
potential energy of an electron moving
between the plates?
0%
0%
0%
0%
0%
1.
2.
3.
4.
5.
1.6 x 10 –19 J
4.8 x 10 –19 J
9.6 x 10 –19 J
1.9 x 10 19 J
5.3 x 10 –20 J
3.0V
Plate X
Plate Y
90
Two parallel metal plates X and Y in a
vacuum have a potential difference V
across them. What is the speed of an
electron of charge e and mass m as it
reaches Y from X?
0%
0%
0%
0%
0%
1. 2eV/m
2. √2eV/m
3. √2V/em
4. 2V/em
5. 2mV/e
X
Y
-
+
V
90
In the circuit below, when the switch is
open V = 2.6V. With the switch closed,
V= 2.2V. This decrease of 0.4 V is
called…
0%
0%
0%
0%
0%
1.
2.
3.
4.
5.
V
Peak voltage
e.m.f.
r.m.s voltage
Lost volts
Terminal potential difference
0%
30
0%
0%
0%
0%
0%
The battery in the circuit below has an
emf of 6.0V and an internal resistance
of 0.20 ohms. What is the resistance
of R if the reading on the ammeter is
4A?
6.0V
1. 1.5 ohms
0.20 
2. 2.2 ohms
A
3. 1.3 ohms
R
4. 0.7 0hms
5. 6.4 ohms
90
What is the p.d. across the 10 
resistor?
0%
0%
0%
0%
0%
1.
2.
3.
4.
5.
1.0V
1.2V
4.8V
5.0V
6.0V
6.0V
2
A
10 
90
The p.d. across the 16 ohm resistor is
40V when the switch is open. What is
the p.d. across the 16 ohm resistor
when S is closed?
0%
0%
0%
0%
0%
1.
2.
3.
4.
5.
12V
15V
30V
45V
48V
60V
8
S
16 
8
90
0%
0%
0%
0%
0%
In the circuit below, each resistor has
a resistance of 20 ohms. What is the
voltage across XY?
1. 3.5V
3.5V
2. 0.2V
3. 2.0V
4. 0.5V
X
Y
5. 1V
90
In the circuit shown, the p.d. between
points P and Q is 12 V. What is the
reading on the voltmeter?
0%
0%
0%
0%
0%
1.
2.
3.
4.
5.
0V
2V
4V
6V
8V
P
2
4
Q
V
4
8
30
In the Wheatstone bridge shown, there
is a small reading on the voltmeter.
What should be done to balance the
bridge?
6
0%
0%
0%
0%
0%
1.
2.
3.
4.
5.
12
Increase P by 6 
Q
P
Increase Q by 6 
R
S
4
12
Increase R by 6 
Increase S by 6 
Insert a 6  resistor in series with
the voltmeter.
V
90
What is the total power developed in
the circuit below?
0%
0%
0%
0%
0%
1.
2.
3.
4.
5.
12W
24W
48W
300W
1200W
12V
6
6
90
In the circuit below, the frequency of
the a.c. supply output is varied in
frequency from 50Hz to 5kHz. What is
the ammeter reading?
0%
0%
0%
0%
0%
1.
2.
3.
4.
5.
Falls steadily
Remains constant
Rises then falls
Rises steadily
Falls then rises
A
1K 
30
A supply with alternating output 6V
r.m.s. is connected as shown. What is
the peak voltage across the resistor
and the peak current in the circuit?
0%
0%
0%
0%
0%
1.
2.
3.
4.
5.
Vp=6√2
Vp=6√2
Vp=6
Vp=6√2
Vp=6
Ip=2√2
Ip=2
Ip=2
Ip=1/(2√2)
Ip=2√2
6V
3 
90
The resistance of the LDR decreases when the light
intensity increases. Which row shows the correct
voltmeter readings when the lights are off?
1.
2.
3.
4.
5.
V1= increases V2 = increases
V1= decreases V3 = increases
V2 = increases V3 = decreases
V2 = no change V3 = decreases
V1= decreases V2 = no change
-
V1
V
+
V2
V3
The peak voltage of a supply is 70V.
What is the r.m.s. value?
99.0V
35.0V
17.5V
49.5V
50.3V
.3
50
.5
49
V
0%
V
0%
V
.5
17
.0
35
.0
0%
V
0%
V
0%
99
1.
2.
3.
4.
5.
90
A student measures the frequency of
an a.c. supply and obtains the trace
below. If the grid has 1cm squares,
what is the frequency of the supply?
0%
0%
0%
0%
0%
1.
2.
3.
4.
5.
0.06Hz
0.17Hz
41.7Hz
62.5Hz
125Hz
Y-gain = 3mV/cm
Timebase = 2ms/cm
90