## Physics (2018) Study Mode

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Question 81
A
Pair of calipers
B
Meter rule
C
Micrometer screw gauge
D
Tape rule
Explanation.

No official Explanation yet!

Question 82
A
Heat dissipation
B
Production of eddy currents
C
Excessive current discharge
D
Excessive voltage discharge
Explanation.

The primary reason that power is transmitted at high voltages is to increase efficiency. As electricity is transmitted over long distances, there are inherent energy losses along the way. High voltage transmission minimizes the amount of power lost as electricity flows from one location to the next. How? The higher the voltage, the lower the current. The lower the current, the lower the resistance losses in the conductors. And when resistance losses are low, energy losses are low also. Electrical engineers consider factors such as the power being transmitted and the distance required for transmission when determining the optimal transmission voltage

Question 83
A

17cm

B

20cm

C

25cm

D

100cm

Explanation.

F = $$\frac{uv}{u + v}$$

20 = $$\frac{100 \times v}{100 + v}$$

v = 25cm

Question 84
A
3.75cm
B
6.70cm
C
10.00cm
D
15.00cm
Explanation.

V = 6cm

M = 6cm

Recall m = U = $$\frac{V}{U}$$

U = $$frac{V}{M}$$

=U = $$\frac{6}{0.6}$$

U = 10

$$\frac{1}{U}$$ + $$\frac{1}{V}$$ = $$\frac{1}{F}$$

$$\frac{1}{10}$$ + $$\frac{1}{6}$$

= $$\frac{1}{F}$$

6 + $$\frac{10}{60}$$

$$\frac{16}{60}$$ = $$\frac{1}{F}$$

F = $$\frac{60}{16}$$

=  3.75cm

Question 85
A
10cm
B
20cm
C
30cm
D
40cm
Explanation.

F= 15cm

M = 3

M = $$\frac{v}{u}$$

V =3u

$$\frac{1}{f}$$ = $$\frac{1}{u}$$ + $$\frac{1}{v}$$

$$\frac{1}{15}$$ = $$\frac{1}{u}$$ - $$\frac{1}{3u}$$

$$\frac{1}{15}$$ =   $$\frac{2}{3u}$$

U =10cm

D = u + v

= 10 +30 = 40cm

Question 86
A
Voltaic cell
B
Emission of electron by incident radiation
C
Emission of protons by incident radiation
D
Photographic plate
Explanation.

No official Explanation yet!

Question 87
A
1.10 Ω
B
1.64 Ω
C
2.44 Ω
D
27.50 Ω
Explanation.

$$\frac{V_1}{V_2}$$ = $$\frac{L_1}{(V_2 − L_1)}$$

$$\frac{R_1}{R_2}$$ = $$\frac{ L_1}{(V_2 − L_1)}$$

$$\frac{2}{R_2}$$ = $$\frac{55}{45}$$

R$$_2$$ = 2 × $$\frac{45}{55}$$
= 1.64Ω

Question 88
A
3,600J
B
6,000J
C
7,200J
D
14,400J
Explanation.

Power drawn by the resistor = IV = (2)(3) = 24W = 24J/s

Energy dissipated = power × time = (24)(5)(60) = 7200J

Question 89
A

0.33

B

0.50

C

1.50

D

3.00

Explanation.

R.d = $$\frac{\text{weight in air}}{\text{apparent loss of weight in water}} = \frac{45}{45 - 15}$$ = $$\frac{45}{30} = 1.50$$

Question 90
A
66m
B
136m
C
264m
D
528m
Explanation.

Distance = speed × time
= (3400) × (0.812)
= 136m

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