# Physics 2018 | Study Mode

Question 41
A
pass through even non-magnetic materials
B
run from the north pole to the south pole
C
are in a state of tension and tend to be shorted
D
intersect one another
##### Explanation

Two magnetic lines of force can not intersect each other.

Question 42
A
Investigation of high voltages
B
Study of electric discharge
C
Operation of X-ray tubes
D
A.C. power transmission
##### Explanation

Question 43
A
4.1$$\Omega$$
B
5.0$$\Omega$$
C
10.8$$\Omega$$
D
11.2$$\Omega$$
##### Explanation

The impedance for a RLC circuit is

$$Z = \sqrt{R^{2} + (X_{L} - X_{C})^{2}}$$

= $$\sqrt{10^{2} + (9 - 4)^{2}}$$

= $$\sqrt{125}$$

= 11.18$$\Omega$$ $$\approxeq$$ 11.2$$\Omega$$

Question 44
A
A
B
B
C
C
D
D
##### Explanation

By convention, the field direction is taken to be outward from the North pole and in to the South pole of the magnet. Also, they form closed lines.

Question 45
A
$$\alpha$$- particles and $$\beta$$- particles
B
$$\alpha$$- particles and X-rays
C
$$\beta$$- particles and X-rays
D
$$\lambda$$- rays and X-rays
##### Explanation

In the course of natural radioactivity, alpha, beta and gamma rays are emitted.

Question 46
A
I, II and IV only
B
I, III and IV only
C
III and IV only
D
I and II only

Question 47
A
Gamma ray
B
C
Infrared ray
D
X-ray
##### Explanation

Radio wave has the longest wavelength and shortest frequency.

Question 48
A
Medicine
B
Oil industry
C
Agriculture
D
Weather forecast

Question 49
A
0.5
B
0.8
C
1.2
D
1.5
##### Explanation

The element B has a mass number of 70 with atomic number 32. Hence, B has 32 protons and (70-32) = 38 neutrons.

The neutron- proton ratio is 38:32 = $$\frac{38}{32} = 1.1875$$

$$\approxeq 1.2$$

Question 50
A
50V
B
100V
C
200V
D
400V
##### Explanation

The ideal transformer (either step-up or step-down) works with the equation:

$$\frac{V_{s}}{V_{p}} = \frac{N_{s}}{N_{p}} = \frac{I_{p}}{I_{s}}$$

where $$V_{s}$$ and $$V_{p}$$ are the voltages applied to the secondary and the primary respectively

$$N_{s}$$ and $$N_{p}$$ are the number of turns on the secondary and primary coils respectively

$$I_{p}$$ and $$I_{s}$$ are the currents flowing in the primary and secondary coils respectively.

$$\frac{V_{s}}{100} = \frac{200}{100}$$

$$V_{s} = \frac{200\times 100}{100} = 200V$$

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