Science Form 3 Chap 7 Exercise Complete)

Electricity 1

Which of the following symbols A, B, C or D is an inductor? A B C D (PMR 2004)

2

The diagram shows an electric circuit.

When the switch is on, what will happen to bulbs M1, M2 and M3? M1

M2

M3

A

Lights up

Does not light up

Lights up

B

Lights up

Lights up

Does not light up

C

Does not light up

Does not light up

Lights up

D

Does not light up

Lights up

Does not light up (PMR 2004)

3

Integrated circuit are used in I

computers

II

handphones

III

calculators

A

I and II only

B

I and III only

C

II and III only

D

I, II and III (PMR 2004)

4

Which of the following diagrams A, B, C or D shows the correct pattern of a magnet field?

(PMR 2004)

5

A group of students carried out an experiment to classify objects as magnetic or non magnetic.

Which the following conclusions are correct? A

Magnetic objects Iron nail Glass rod Copper screw Plastic spoon

B

Magnetic objects Iron nail Copper screw

C

Magnetic objects Iron nail Nickel coin

D

Magnetic objects Glass rod Nickel coin

Non magnetic objects Nickel coin

Non magnetic objects Nickel coin Plastic spoon Glass rod Non magnetic objects Glass rod Plastic spoon Copper screw Non magnetic objects Copper screw Plastic spoon Iron nail (PMR 2004)

6

Which fuse in the circuits A, B, C or D, does not melt when the switch is on?

(PMR 2004)

7

The diagram shows a negatively charged electroscope.

A negatively charged plastic ruler is brought closer to the metal cap. Which of the following is true about the piece of gold leaf in the electroscope? A

It diverges more

B

It diverges and later gets closer again

C

It gets closer to the metal plate

D

Its divergence does not change (PMR 2005)

8

The diagram shows four positions of compasses J, K, L and M. They are placed near to a solenoid that is wound around an iron rod.

Which of the following shows the correct direction of the compass needle? A

J and M

B

J and L

C

K and M

D

K and L (PMR 2005)

9

The diagram shows polystyrene balls, P, Q R and S that have been charged through friction and hung in pairs.

What conclusion can be made about the charges of balls P, Q, R and S? P

Q

R

S

A

Negative

Negative

Positive

Positive

B

Negative

Positive

Negative

Negative

C

Positive

Negative

Negative

Negative

D

Positive

Positive

Negative

Negative (PMR 2005)

10

Diagram 22 shows a complete electric circuit. Bulb R does not light up when bulb S is burnt out.

Diagram 22 Which of the following statements correctly explains the situation? A

The resistance in bulb R is too high

B

The voltage across bulb R is too low

C

Bulb R and bulb S are connected in series

D

Electric current decreases as it flows through the circuit (PMR 2006)

11

A balloon which has been rubbed with a piece of cotton cloth is attracted to a positively charged ruler. This situation occurs because the balloon A

release negative charges

B

receives negative charges

C

has the same positive charges as the ruler

D

has more positive charges than the ruler PMR 2007

12

Diagram 23 shows a circuit where one of the bulbs has fused. This will prevent the other three bulbs from lighting up.

Diagram 23 Which bulb shown in the circuit is fused? A

K

B

L

C

M

D

N PMR 2007

13

Diagram 21 shows four symbols for a circuit diagram.

Diagram 21 Diagram 22 shows a complete circuit.

Diagram 22 Which combination of the symbols would be the most suitable to measure the resistance of a bulb in the complete circuit in diagram 22?

PMR 2007

14

Diagram 19 shows a complete electrical circuit.

Diagram 19 Calculate the total resistance. A

0.4 Ω

B

1.2 Ω

C

5.0 Ω

D

6.0 Ω PMR 2008

16

Diagram 20 shows a parallel circuit with three identical bulbs, P, Q and R.

Diagram 20 What is the voltmeter reading across P if Q burns out? A 0V B

4V

C

6V

D

12 V PMR 2008

Paper 2

1

(a) A night market fruit seller found that a bulb at his stall is brighter when using a shorter wire. (PMR 2005)

Shorter wire Figure 2.1

Longer wire

Figure 2.2

(i)

Based on the observations in Figure 2.1 and 2.2, state the difference in the brightness of the bulb. ................................................................................................................................. ................................................................................................................................ (1 mark)

(ii) What inference can be made based on Figures 2.1 and 1.2? ................................................................................................................................ ................................................................................................................................ (1 mark) (iii) State your hypothesis based on your observations in Figures 2.1 and 2.2. ............................................................................................................................... ................................................................................................................................. (1 mark)

(b) A pupil carries out an experiment to investigate the situation in Figures 2.1 and 2.2. Figure 2.3 shows the arrangement of apparatus for the experiment.

Figure 2.3 The pupil takes the following steps: Step 1 : Touch jockey at Q on the nichrome wire where the distance between and Q is 30 cm. Step 2 : Switch on and record the ammeter reading. Step 3 : Repeat step 1 and step 2 by using nichrome wire with the lengths of 50 cm, 60 cm and 70 cm respectively. (b) (i) Record the ammeter reading in the space provided. The length of nichrome wire = 30 cm Ammeter reading = 0.72 A

40 cm,

The length of nichrome wire = 40 cm Ammeter reading = .................A

The length of nichrome wire = 50 cm Ammeter reading = .................A

The length of nichrome wire = 60 cm Ammeter reading = ..................A

The length of nichrome wire = 70 cm Ammeter reading = .................A

(2 marks) (ii) Complete Table 2.4 by recording the ammeter reading on the respective length of the nichrome wire. Length of nichrome wire / cm Ammeter reading / A

30 0.72 Table 2.4

40 .........

50 ..........

60 .........

70 .........

(c) Using Table 2.4, draw a graph of current against length of wire.

(2 marks) (d) State the relationship between the length of wire and the current. .................................................................................................................................. .................................................................................................................................. (1 mark) (e) State the variables involved in this experiment. Manipulated variable

...............................................................

Responding variable

...............................................................

Controlled variable

Type of wire, number of dry cells, thickness of wire. (2 marks)

(f) Based on the graph in (c), predict the ammeter reading for a nichrome wire with the length of 80 cm. …………………………………………………………………………………….. (1 mark) (g) Based on the experiment, state the relationship between the brightness of the bulb and current. ………………………………………………………………………………………… ………………………………………………………………………………………… (1 mark) 2

Diagram 4.1 shows the apparatus set-up apparatus for an electric circuit to study the relationship between voltage, current and resistance. (PMR 2007)

X

Y

Z Diagram 4.1

(a) What is apparatus Z? ………………………………………………………………………………………………… (1 mark)

(b) State the function of X and Y. Apparatus X

Function ………………………………………………………………….. ………………………………………………………………….. …………………………………………………………………..

Y …………………………………………………………………..

(c) Based on Diagram 4.1 suggest one way to reduce the reading of apparatus Z. ……………………………………………………………………………………………….. ……………………………………………………………………………………………….. (1 mark)

(d) Diagram 4.2 shows a parallel circuit.

A M1

M2

Diagram 4.2 M1 and M2 are two identical bulbs. The resistance of each bulb is 2 ohms and the current in the circuit is 6 A. Calculate the voltage in the circuit.

3

(a) Diagram 4.1 shows a parallel circuit with three identical bulbs, J, K and L. (PMR 2008)

Diagram 4.1

(i)

State the brightness of all the bulbs, if the switch in this circuit is on. ………………………………………………………………………………… (1 mark)

(ii)

Give one reason for the answer in 4 (a)(i) …………………………………………………………………………………. …………………………………………………………………………………. (1 mark)

(iii)

If J is removed, what happen to K and L? ………………………………………………………………………………….. ………………………………………………………………………………….. (1 mark)

(iv)

If the parallel circuit is replaced by a series circuit, what happen to the other bulbs if one of the bulbs burns out? …………………………………………………………………………………… …………………………………………………………………………………… (1 mark)

(b) Diagram 4.2 shows a complete electrical circuit. The metal paper clip is moved along the wire from M to N.

Diagram 4.2

(i)

What happens to the ammeter reading as the clip moves along the wire from M to N? …………………………………………………………………………………… (1 mark)

(ii)

Give one reason fro the answer in 4 (b) (i) ……………………………………………………………………………………. ……………………………………………………………………………………. (1 mark)

Electricity Paper 1 1. A 2. A 3. D 4. C 5. B 6. B 7. A 8. B 9. B 10. C 11. B 12. C 13. B 14. C

Paper 2 No. 1

Answers scheme a. (i) The bulb in figure 8.1 is brighter than the bulb in figure 8.2. (ii) The brightness of the bulb depends on the length of the wire (iii) The shorter the wire, the brighter the bulb. b. (i) 40 cm - Ammeter reading = 0.67A 50 cm - Ammeter reading = 0.62A 60 cm - Ammeter reading = 0.57A 70 cm - Ammeter reading = 0.52A

(ii) Length of nichrome wire / cm

30

40

50

60

70

Ammeter reading / A

0.72

0.67

0.62

0.57

0.52

d. The longer the wire the smaller the current flow. e. Manipulated variable: Length of nichrome wire Responding variable: Ammeter reading/current. f. 0.47 A g. The higher the current flow, the brighter the bulb shine. 2

a. Ammeter b. X = To measure the voltage. Y = It changes the values of resistance in the circuit and hence the current that flows through the circuit. c. Adjust Y to a higher value./ Reduce the number of cells.

d. 1 = 1 + 1 R 2 2 1 = R total

2

R total = 1Ω

V = IR V = (6A)(1 Ω) =6V 3

a. (i) J, K and L have the same brightness. (ii) Because the voltage received by bulb J, K and L is the same. (iii) Bulb K and L will continue to light up. (iv) In series circuit if one bulb burns, all of the other bulb will not light up. b. (i) The reading will reduce/decrease. (ii) Because the resistance has increase by moving the metal clip which will decrease the reading of the Ammeter.