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At room temperature, a P-type semiconductor has
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(a) Large number of holes and few electrons |
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(b) Large number of free electrons and few holes |
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(c) Equal number of free electrons and holes |
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(d) No electrons or holes |
A hydrogen like atom of atomic number Z is in an excited state of quantum number 2n. It can emit a maximum energy photon of 204 eV. If it makes a transition to quantum state n, a photon of energy 40.8 eV is emitted. The value of n will be
|
(a) 1 |
(b) 2 |
(c) 3 |
(d) 4 |
A parallel plate capacitor with air as medium between the plates has a capacitance of 10 μF. The area of capacitor is divided into two equal halves and filled with two media as shown in the figure having dielectric constant 
and 
. The capacitance of the system will now be
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(a) 10 μF |
(b) 20 μF |
(c) 30 μF |
(d) 40 μF |
The effective resistance between points A and B is
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(a) 10 Ω |
(b) 20 Ω |
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(c) 40 Ω |
(d) None of the above three values |
You are given a resistance wire of length 50 cm and a battery of negligible resistance. In which of the following cases is largest amount of heat generated
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(a) When the wire is connected to the battery directly |
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(b) When the wire is divided into two parts and both the parts connected to the battery in parallel |
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(c) When the wire is divided into four parts and all the four connected to the battery in parallel |
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(d) When only half the wire is connected to the battery |
A charge Q is divided into two parts of q and Q - q. If the coulomb repulsion between them when they are separated is to be maximum, the ratio of 
should be
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(a) 2 |
(b) 1/2 |
(c) 4 |
(d) 1/4 |
The resistance of a conductor is 5 ohm at 50 oC and 6 ohm at 100 oC. Its resistance at 0 oC is
|
(a) 1 ohm |
(b) 2 ohm |
(c) 3 ohm |
(d) 4 ohm |