A step-down transformer is used on a 1000 V line to deliver 20 A at 120 V at the secondary coil. If the efficiency of the transformer is 80%, the current drawn from the line is
1. 3 A
2. 30 A
3. 0.3 A
4. 2.4 A
A step-down transformer is used on a 1000 V line to deliver 20 A at 120 V at the secondary coil. If the efficiency of the transformer is 80%, the current drawn from the line is
1. 3 A
2. 30 A
3. 0.3 A
4. 2.4 A
Subtopic: Transformer |
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What kV potential is to be applied on X-ray tube so that minimum wavelength of emitted X-rays may be 1 Å (h = 6.6×10-34 J-s)
1. 12.42 kV
2. 12.84 kV
3. 11.98 kV
4. 10.78 kV
Subtopic: X-Ray (OLD NCERT) |
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Hydrogen atom excites energy level from fundamental state to n =3. Number of spectrum lines according to Bohr is
1. 4
2. 3
3. 1
4. 2
Subtopic: Bohr's Model of Atom |
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A black body at a temperature of 2600 K has the wavelength corresponding to maximum emission 1200Å. Assuming the moon to be perfectly black body the temperature of the moon, if the wavelength corresponding to maximum emission if 5000 Å is
1. 7800 K
2. 6240 K
3. 5240 K
4. 3640 K
Subtopic: Wien's Displacement Law |
66%
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The heat required to increase the temperature of 4 moles of a monoatomic ideal gas from 273 K to 473 K at constant volume is
1. 200 R
2. 400 R
3. 800 R
4. 1200 R
Subtopic: Molar Specific Heat |
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A solid sphere rolls without slipping on the roof. The ratio of its rotational kinetic energy and its total kinetic energy is
1. 2/5
2. 4/5
3. 2/7
4. 3/7
Subtopic: Rolling Motion (OLD NCERT) |
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6Ω and 12Ω resistors are connected in parallel. This combination is connected in series with a 10 V battery and 6Ω resistor. What is the potential difference between the terminals of the 12Ω resistor?
1. 4 V
2. 16 V
3. 2
4. 8 V
Subtopic: EMF & Terminal Voltage |
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Charge passing through a conductor of cross section area A = 0.3m2 is given by q = 3t2 +5t+2 in coulomb, where t is in second. What is the value of drift velocity at t = 2s? (Given, n = 2×1025/m3)
Subtopic: Current & Current Density |
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Assertion When a body is dropped or thrown horizontally from the same height, it would reach the ground at the same time.
Reason Horizontal velocity has no effect on the vertical direction.
- If both the assertion and the reason are true and the reason is a correct explanation of the assertion
- If both the assertion and reason are true but the reason is not a correct explanation of the assertion
- If the assertion is true but the reason is false
- If both the assertion and reason are false
Subtopic: Projectile Motion |
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Assertion Two similar trains are moving along the equatorial line with the same speed but in opposite direction. They will exert equal pressure on the rails.
Reason In uniform circular motion the magnitude of acceleration remains constant but the direction continuously changes.
Reason In uniform circular motion the magnitude of acceleration remains constant but the direction continuously changes.
1. Both Assertion and Reason are true and the Reason is the correct explanation of the Assertion.
2. Both Assertion and Reason are true but the Reason is not the correct explanation of the Assertion.
3. Assertion is true but Reason is false.
4. Assertion is false but Reason is true.
Subtopic: Circular Motion |
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