# A steel wire of $$1~\mathrm{m}$$ long and $$1~\mathrm{mm^2}$$ cross-section area is hanged from a rigid end when the weight of $$1~\mathrm{kg}$$ is hung from it, then the change in the length will be: (Young’s coefficient for wire $$\mathrm{Y}=2 \times 10^{11} \mathrm{~N} / \mathrm{m}^2$$) 1. $$0.5 \mathrm{~mm}$$ 2. $$0.25 \mathrm{~mm}$$ 3. $$0.05 \mathrm{~mm}$$ 4. $$5 \mathrm{~mm}$$

Subtopic:  Stress - Strain |
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When plate voltage in diode valve is increased from 100 V to 150 V. Then, the plate increases from 7.5 mA to 12 mA, then dynamic plate resistance will be:
1. $$10~\mathrm{k\Omega}$$
2. $$11~\mathrm{k\Omega}$$
3. $$15~\mathrm{k\Omega}$$
4. $$11.1~\mathrm{k\Omega}$$

Subtopic:  PN junction |
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If the sun rays are indenting at $$60^\circ$$ angle and intensity is $$I.$$ If the sun rays are made incident at $$30^\circ$$ angle, then what will be the intensity?
1. $$\frac{I}{\sqrt3}$$
2. $$\sqrt3 I$$
3. $$3I$$
4. $$\frac{I}{3}$$

Subtopic:  Superposition Principle |
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From NCERT
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The reason for current flow in the p-n junction in forward bias is:

 1 drifting of charge carriers 2 drifting of minority charge carriers 3 diffusion of charge carriers 4 all of the above

Subtopic:  PN junction |
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A charged particle is accelerated by a potential of 200 V. If its velocity is 8.4 × 108 m/s, then the value of e/m for that particle is:
1. 17.6 × 1016
2. 14.5 × 1012
3. 1.76 × 1015
4. 1.45 × 1015

Subtopic:  Electric Field |
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When an open organ is dipped in water up to half of its height, then its frequency will become:
1. half
2. double
3. remain same
4. four times

Subtopic:  Standing Waves |
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A sound source producing waves of frequency 300 Hz and wavelength 1 m observer is stationary, while the source is going away with the velocity 30 m/s, then apparent frequency heard by the observer is:

1. 270 Hz

2. 273 Hz

3. 383 Hz

4. 300 Hz

Subtopic:  Doppler's Effect (OLD NCERT) |
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A particle moves towards east for 2 s with velocity 15 m/s and move towards north for 8 s with velocity 5 m/s. Then, the average velocity of the particle is:

1. 2 m/s

2. 5 m/s

3. 7 m/s

4. 10 m/s

Subtopic:  Average Speed & Average Velocity |
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Relation between a wavelength of photon and electron of same energy is:
1. $$\lambda_{p h}>\lambda_e$$
2. $$\lambda_{p h}<\lambda_e$$
3. $$\lambda_{p h}=\lambda_e$$
4. $$\frac{\lambda_e}{\lambda_{p h}}=\text { constant }$$

Subtopic:  De-broglie Wavelength |
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Match the following.

 A. Angular momentum 1 [M-1L2T-2] B. Torque 2 [M1T-2] C. Gravitational constant 3 [M1L2T-2] D. Tension 4 [M1L2T-1]

1. C-2, D-1
2. A-4, B-3
3. A-3, C-2
4. B-2, A-1

Subtopic:  Dimensions |
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