Intermediate 1 Physics

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Intermediate 1 Physics . Practical Electricity. Questions and Answers. Intermediate 1 Physics . Practical Electricity. Questions 1 to 10. Questions 11 to 20. Questions 21 to 30. Questions 31 to 40. Questions 41 to 46. M. V. voltmeter = .

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### Intermediate 1 Physics

Practical Electricity

Questions

and

Beath High School - Int 1 Physics

### Intermediate 1 Physics

Practical Electricity

Questions 1 to 10

Questions 11 to 20

Questions 21 to 30

Questions 31 to 40

Questions 41 to 46

Beath High School - Int 1 Physics

M

V

voltmeter =

1. Draw the circuit symbols for, a voltmeter; an electric motor; a switch and a fuse.

electric motor =

switch =

fuse =

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A

battery

supplies energy

2. Beside each of the following symbols write the name of the component and state what it does.

lamp

changes electrical energy

to light energy

fixed resistor

opposes current and

produces heat

variable resistor

controls current

ammeter

measures current

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3. Draw circuit diagrams showing:

(a) a battery, a lamp and two resistors all in series

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A

3. Draw circuit diagrams showing:

(b) a battery, two lamps, a switch and an ammeter all in series

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3. Draw circuit diagrams showing:

(c) a battery and three lamps in parallel

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3. Draw circuit diagrams showing:

(d) a battery and switch in series, connected to three resistors in parallel with each other.

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A

4. Redraw the circuit below showing how to measure the current through the lamp.

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V

5. Redraw the circuit of question 4 showing how to measure the voltage across the lamp.

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A

A

A

6. Write the reading of the ammeters beside each ammeter symbol.

0.9A

0.9A

0.9A

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V

7. Redraw the circuit of question 6 without the ammeters and show how you would connect a voltmeter to measure the supply voltage

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8. In the circuit below, the lamps are identical and the current through each lamp is 0.6 A.

Mark beside each component the value of the current through it.

0.6A

0.6A

1.2A

1.2A

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A

9. In the circuit below the ammeter reads 0.6 amperes.

What is the value of the current through the lamp?.

0.6A

0.6A

because the current is the same everywhere in a series circuit

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A2

A1

battery

10. In the circuit below, ammeter A1 reads 0.2 amperes and ammeter A2 reads 0.5 amperes.

Beside each component, write its name and the value of the current through it.

0.5A

lamp

0.5A

0.5A

0.2A

resistor

0.2A

heater

0.3A

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V

A2

A1

11. Redraw the circuit of question 10 and show how the voltage across the lamp can be measured.

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V

8.0V

12. In this circuit, the lamps are different.

What is the voltage across the other lamp L2?

L2

3.0V

= 8.0V – 3.0V

= 5.0V

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V

13. In the circuit below, the voltmeter reads 4 volts.

What is the voltage across the resistor R?

the voltage is the same across components which are in parallel.

R

the voltage across R = 4 volts

4 volts

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V

V

Vsupply =

4V + 6V

= 10V

14. In the circuit below, the voltages are as shown.

What is the voltage of the supply?

4V

6V

voltages in a series circuit add up to the supply voltage.

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V

V

24V

15. In the circuit below, the voltages are shown. What is the voltage across the second resistor?

8V

Vresistor =

24V - 8V

= 16V

voltages in a series circuit add up to the supply voltage.

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24V

16. This diagram shows a 6 V bulb working correctly off a 24 V supply. What must be the voltage across the resistor?

Vresistor =

24V - 6V

6V

= 18V

voltages in a series circuit add up to the supply voltage.

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courtesy light

17. The diagram shows the circuit of the courtesy light in a two-door car.

A car courtesy light

operates when either door

of the car is opened.

(a) What happens to a switch when a door is opened?

(b) Explain why the switches are in parallel rather than in series.

S1

S2

The switch closes (and completes the circuit).

This means that when either door is opened, the circuit is completed and so the courtesy lamp lights.

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voltage

current

resistance =

18. A resistor has a voltage across it of 12 volts and a current through it of 2 amperes.

Calculate the resistance of the resistor.

12

=

2

=

6W

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voltage

current

resistance =

19. A voltage of 6 volts is across a resistor where the current is 0.5 amperes.

What is the value of the resistor?

6

=

0.5

=

12W

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voltage

current

resistance =

20. Calculate the resistance of a component when a voltage of 24 V causes a current of 0.1 amperes.

24

=

0.1

=

240W

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voltage

current

resistance =

21. If a current of 2 amperes exists through a lamp when it has 12 volts across it, what is the resistance of the lamp?

12

=

2

=

6W

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voltage

current

resistance =

22. A torch bulb is marked "6 V, 0.25 A".

Calculate the resistance of the bulb.

6

=

0.25

=

24W

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voltage

current

23. A resistor is placed in a circuit. The voltage across it and current through it are measured as 12 volts and 0.02 amperes.

The resistor is now removed from the circuit and an ohmmeter connected across it.

What is the reading on the ohmmeter?

resistance =

12

=

0.02

=

600W

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V

V

V

2V

3V

5V

24. (a) Find the values of the resistors in the circuit

below.

R1

R2

R3

0.25A

V

2

V

5

R1 =

=

=

8W

R3 =

=

=

20W

I

0.25

I

0.25

V

3

R2 =

=

=

12W

I

0.25

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V

V

V

2V

3V

5V

24. (b) Calculate the value of the supply voltage.

R1

R2

R3

0.25A

voltages in a series circuit add up to the supply voltage.

so, Vsupply =

2V + 3V + 5V

= 10V

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The human body conducts better when wet.

It is therefore more likely that you could be electrocuted,

25. Explain why it is dangerous to operate mains switches with wet hands.

and mains voltage can cause a current large enough to kill you.

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Hold the terminals of an ohmmeter in separate hands.

26. Describe an experiment to show the change in conductivity of the human body when it is dry or wet.

Wet your hands and repeat the experiment.

Your resistance will have reduced showing that your body is a better conductor when it is wet.

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cable grip

e a r t h

27. Draw a sketch of a domestic three-pin plug.

Label the wires; live, neutral and earth and state the colours of their insulation.

Label the fuse and describe how it works.

y e l l o w

b r o w n

u s e

b l u e

l i v e

n e u t r a l

The fuse is a wire which melts and breaks the circuit if too high a current flows.

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28. Draw the symbol for a double insulated appliance.

Describe what is meant by "double insulated".

A double insulated appliance has an insulated casing which cannot become ‘live’.

You cannot be electrocuted touching its casing and so it does not need an earth wire.

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29. What are the advantages of using a circuit breaker instead of a fuse?

• A circuit breaker is easier to reset than rewiring a fuse

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power

current =

=

voltage

1150

= 5A

230

30. Which fuse value is required for an appliance with a power of 1150 watts?

Therefore a 13 ampere fuse is required.

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power

current =

=

voltage

820

= 3.6A

230

31. A mains appliance has a power rating of 820 watts. How much current does it require?

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power

current =

=

voltage

2000

= 8.7A

230

32. How much current will a 2 kilowatt mains heater require?

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power

current =

=

voltage

33. Mains plugs can have a choice of two values; 3 A and 13 A.

Which fuse should be inserted in a plug attached to a 750 watt appliance?

750

= 3.3A

230

A 3A fuse would be too low as it would

be melted by a current of 3.3A.

Therefore a 13 ampere fuse is required.

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power

current =

=

voltage

34. A lighting circuit in a house serves 6 rooms. If each room can have a maximum of 150 watts per ceiling lamp, what value of fuse should be used to protect the circuit?

6 x 150

230

900

=

230

= 3.9A

Therefore a 5 ampere fuse is suitable

for this lighting circuit.

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flexes

live

35. Complete the following sentences to make 4 important safety rules for mains electricity.

(a) Never use worn or damaged : you could get a shock from an exposed wire.

(b) Avoid the use of if possible: too many appliances connected to an adaptor could produce at the socket.

(c) Always use the correct flex: a flex which is

too could overheat.

(d) Always use the correct plug : if the fuse rating is too and a fault develops, the flex could overheat.

extensions

overheating

thin

fuse

high

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The circuit is broken (i.e. an open circuit) if the reading is “off scale” (i.e. 1 . ).

Set the multimeter to be an ohmmeter (i.e. a resistance meter).

36. Describe how to use a multimeter to detect an open circuit. Make sure you include how to set the multimeter to the correct setting and what you would expect to see for this fault.

Connect the ohmmeter to the circuit.

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37. The circuit shown below contains a battery, lamp, 1 A fuse and a variable resistor.

(a) Is this a series or a parallel circuit?

series

; because there is only one path for current.

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37. (b)The variable resistor is set so that a current of

2A flows.

(i) What happens to the fuse when

there is a current of 2 A?

(ii) What happens to the lamp when

there is a current of 2 A in the

It melts/breaks/blows.

(This is because it allows a maximum current of 1A.)

The lamp stops lighting/goes off.

This is because, when the fuse melts, the circuit is broken and so the current stops.

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38. A group of pupils investigate the time various appliances are switched on for during a day.

The appliances are all rated at 100 W.

Their results are presented in the bar chart below.

(a) Which of the appliances is switched on for the

longest time?

The lamp,

because its bar is the highest.

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The lamp,

38. (b) All of the appliances have a power rating of 100W.

Explain which of the appliances is most costly to

use in one day.

because, being on for longer, it uses more electrical energy than the other appliances.

You should note that a higher powered appliance (like a heater) can cost more to use even if it is on for a shorter time.

This is because it is using electrical energy at a faster rate.

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39. The following table gives details about various household appliances.

(a) Complete the table shown above.

(b) List all the appliances in the table which should

have a 3 A fuse fitted in their plug.

0.26A

8.7A

7.8A

1.3A

The table lamp

and the curling tongs.

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A1

A2

40. Shown below is a parallel circuit containing a battery, resistor, lamp and two ammeters.

taken from the ammeters:

Reading on A1 = 0.05 A

Reading on A2 = 0.42 A

(a) State the current through the lamp.

(b) Which component, the resistor or the lamp, has

0.42A

the resistor

It has a smaller current through it.

The current has split with most of it taking the easier path through the lamp.

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power

4

current =

=

= 0.017A

voltage

230

41. The adverts shown below give information on two music systems.

(a) Explain which music system is the more expensive to operate.

(b) Both of these systems need to be connected to the mains supply. State the voltage across these systems when connected to the mains.

(c) Calculate the current in the ‘Pony’ music system.

The VMJ one as it has a higher power rating.

230V

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42. A continuity tester is shown.

(a) A piece of bare copper wire is connected to both metal probes. Will the lamp light?

Yes,

because the thick copper has a very low resistance and completes the circuit.

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42. (b) The circuit below contains 2 copper wires covered in plastic and a heater.

A test engineer suspects that there is an open circuit fault.

Describe how the continuity tester can be used to test if there is an open circuit.

Set the multimeter to be an ohmmeter (i.e. a resistance meter).

Connect the ohmmeter to the two terminals.

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42. (c) The continuity tester is connected to the L and N

pins of the plug of the appliance shown below.

The lamp does not light.

Complete the following sentences:

Since the lamp does not light this must be an circuit.

This could be because there is a wire or the on/off switch is in the position.

open

broken

off

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XPOWER

battery

A

V

resistance =

43. A car accessory shop sells a hand held search lamp which works with a car battery.

A motorist buys the hand held search lamp and decides to check its resistance.

(a) Complete the diagram below to show how this could

be done using an ammeter and voltmeter.

(b) How would the motorist use the readings to find

the resistance of the search lamp? (SEB 1990)

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44. The diagram shows the wire of a food processor

correctly connected to a three pin plug.

(a) Complete the table below naming the colour of the

insulation on the wires connected to pins L and N.

(b) One pin of the plug has not been used because the food processor is double insulated.

(i) What name is given to the pin which has not

been used?

(ii) Draw the double insulation symbol. (SEB 1990)

brown

blue

earth

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V

A

Set 1

Set 2

Set 3

Set 4

Voltage

6

6

6

6

(volts)

Current

0.1

0.2

0.3

0.4

(amperes)

45. The circuit shown is used to investigate the effect of a variable resistor in a circuit.

The variable resistor setting is gradually changed.

The readings taken from the meters are shown in the table below.

Set 1 was the first set of readings, set 2 the second, etc.

The readings were taken in the order shown.

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voltage

current

Its resistance was decreased;

45. (a) Was the resistance of the variable resistor

increased or decreased during the experiment?

(b) Calculate the resistance at the lowest setting of

the variable resistor in this experiment.

the current was increasing showing that it was becoming easier for current to flow.

resistance =

6

=

0.4

=

15W

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46. Various appliances and the value of the fuse they need are listed below.

Computer: 3 A, Toaster: 13 A, Hair dryer: 13 A, CD player: 3 A, Coffee percolator: 3 A, Vacuum cleaner: 13 A.

Construct a table, with suitable headings, which lists the appliances in two groups. One group should contain those appliances requiring a 3 A fuse. The second group should contain those appliances requiring a 13 A fuse.

Appliances using 3A fuse

Appliances using 13A fuse

Computer

Toaster

CD player

Hair dryer

Coffee percolator

Vacuum cleaner

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### Intermediate 1 Physics

Practical Electricity

End of

Questions and