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1. What is the current flowing in a circuit if 30C are passed in 1
minute?
Q = It
30 = I x 60
I = 30/60
0.5A
answer
2. What voltage would be measured over a 100 Ω resistor when 10mA
flows through it?
V = IR
V = 0.01 x 100
1V
answer
3. How many joules of energy are transferred by a 60W bulb every second?
P = E/t
60 = E/1
E =60/1
60J
answer
4. Calculate the size of the current flowing in a 3kW mains operated appliance.
answer
13A
5. A television draws 0.1 A and has a resistance of 5000Ω. Calculate the
power consumption
P = IV
P = 0.1 x 5000
50W
answer
6. How many 1.5V bulbs operating at their correct voltage could be connected
in series with a 6V cell?
Vs = V1+ V2…6 = 1.5 +1.5 + 1.5 +1.5
6 = 4(1.5)Four bulbs
answer
7. What is the total resistance of a set of Christmas lights comprising of 30
individual 10Ω lamps in series?
Rt = R1+R2+…
Rt= 30(10)
3600 Ω or 3.6kΩ
answer
8. An electrical supply for a caravan delivers a total current of 2A to the fridge
and lighting circuits. If the lights use 0.25A, what is the operating current of the
fridge?
It = Ilights+Ifridge
2= 0.25 + Ifridge
I fridge = 2 - 0.25
1.75A
answer
9.What is the total resistance of three 90Ω resistors connected in
parallel?
1/Rt = 1/R1+1/R2+1/R3
1/Rt = 1/90+1/90+1/90
1/Rt = 3/90
Rt = 90/3
30 Ω
answer
10. Work out the enegy used in kWhr for a 2000 W electric heater which is used for 45 mins?
E = Pt
E= 2(kW)x 0.75(hr)
1.5kWhr
answer
11. How many joules are used if a tumble dryer uses 0.75 kWh?
750Whr750J/s(hr)750x3600
2700kJ or 2700000J
answer
12. Select the appropriate formula from your data book..
That shows the relationship between charge, current and time.
Q=It
answer
13. Select the appropriate formula from your data book..
That shows the relationship between voltage, current and resistance.
V = IR
answer
14. State Ohm’s Law.
V = IR
answer
15.
Rt = R1+R2+R3
answer
Select the appropriate formula from your data book..To calculate resistances in series.
16.
1/Rt= 1/R1 +1/R2 + 1/R3
answer
Select the appropriate formula from your data book..For combining resistors in parallel.
17. State the relationship between Energy and Power
P = E/t
answer
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