MCQ
The reason for attractive force between two parallel wires in which current is flowing in same direction is:
- Aelectromotive force between them
- Bmutual inductance between them
- Celectric force between them
- ✓magnetic force between them
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A wire of length L and 3 identical cells of negligible internal resistances are connected in series. Due to current, the temperature of the wire is raised by ∆ T in a time t. A number N of similar cells is now connected in series with a wire of the same material and cross – section but of length 2 L. The temperature of the wire is raised by the same amount ∆ T in the same time t. the value of N is
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(a) 4 |
(b) 6 |
(c) 8 |
(d) 9 |
In X-ray tube when the accelerating voltage V is halved, the difference between the wavelength of Ka line and minimum wavelength of continuous X-ray spectrum
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(a) Remains constant |
(b) Becomes more than two times |
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(c) Becomes half |
(d) Becomes less than two times |
Assertion : Short wave bands are used for transmission of radio waves to a large distance.
Reason : Short waves are reflected by ionosphere
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(a) If both assertion and reason are true and the reason is the correct explanation of the assertion. |
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(b) If both assertion and reason are true but reason is not the correct explanation of the assertion. |
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(c) If assertion is true but reason is false. |
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(d) If the assertion and reason both are false. |
If the temperature of cold junction of thermocouple is lowered, then the neutral temperature
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(a) Increases |
(b) Approaches inversion temperature |
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(c) Decreases |
(d) Remains the same |
Assertion : The number of electrons in a P-type silicon semiconductor is less than the number of electrons in a pure silicon semiconductor at room temperature.
Reason : It is due to law of mass action.
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(a) If both assertion and reason are true and the reason is the correct explanation of the assertion. |
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(b) If both assertion and reason are true but reason is not the correct explanation of the assertion. |
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(c) If assertion is true but reason is false. |
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(d) If the assertion and reason both are false. |
The temperature at which thermal electric power of a thermo couple becomes zero is called
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(a) Inversion temperature |
(b) Neutral temperature |
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(c) Junction temperature |
(d) Null temperature |