Transcript N45 Electricity 1 20Q

Twenty Questions
Electricity 1
Twenty Questions
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20
1. State the relationship for
current in a Series circuit.
• Current is the same at
all points in a series
circuit.
•I1 = I2 = I3
2. What effect does increasing the
resistance of a circuit have on the
current?
• As resistance
increases current
decreases.
3. In which position is the
voltmeter/ammeter?
A
V
4. Calculate the
total resistance.
20Ω
10Ω
5Ω
1
1
1
1
1



  0.05  0.2  0.25
RT
RT
RT
20 5
RT
1

 4
1
0.25
RT  10  4  14
5. Two identical bulbs are connected in
series to a 9V battery.
What is the voltage across each bulb?
• 9/2= 4.5V
6. Calculate the power dissipated in
a 330Ω resistor when a 5A current
flows through it.
2
I
•P=
R
2
• P = (5) x 330
• P = 8250W
7. Two identical 10Ω resistors are
connected to a 9V supply. What is the
current through each resistor?
• R = 10 + 10 = 20Ω
• I=V/R=9/20
• I = 0.45A
8. State the relationship for
voltage in a parallel circuit.
• Voltage in a parallel
circuit is equal across
each branch.
VT = V1 = V2 = V3
9. What is electrical power?
• The rate at which
electrical energy is
converted to other
forms.
• Energy per second
10. What is the function of a
variable resistor?
• To allow you to vary
the current in a circuit.
11. Which resistor has a greater
potential difference across it?
• The 7Ω
resistor.
9V
7Ω
6Ω
12. Calculate the voltage
across the resistor.
• Vs = V1 + V2
• 12 = 4 + V2
• V2 = 8V
12V
4V
13. What is current?
•The rate of flow of
electric charges
around a circuit.
• The charge per
second that passes a
point.
14. What happens to the value of a
resistor when the Voltage across it
is increased?
• The resistance of a
resistor remains
constant.
15. Give a practical application of a
variable resistor.
• Volume control on radio
• Temperature control
on cooker
• Brightness control on a
dimmer switch
16. What is the current
through the bulb?
• IT = I1 + I2
• 4 = 3 + I2
• I2 = 1A
4A
3A
17. What is the total resistance of a
20Ω & 30 Ω resistor in parallel?
1
1
1


RT
RT
RT
1
1
1


RT
20 30
1
 0.05  0.033  0.083
RT
RT
1

 12
1
0.083
18. Calculate the energy used by a
12V kettle in 2minutes if it draws
3A from it’s supply.
• P = IV = 3x12 = 36W
E = Pt
E = 36x2x60
E = 4320J
19. What formula relates power,
voltage and resistance?
•P=
2
V /R
20. What is Voltage?
•The energy given
to each charge in
the circuit.