- AProduct of A and B is Y
- BY exists when A exists or B exists
- CY exists when both A and B exist but not when only A or B exists
- DY exists when A or B exists but not both A and B exist.
Explanation:
In Boolean algebra A.B = Y implies that Y exists when both A and B exist but not when only A or B exists.
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n identical cells each of e.m.f. E and internal resistance r are connected in series. An external resistance R is connected in series to this combination. The current through R is
|
(a) |
(b) |
(c) |
(d) |
A sample contains 16 gm of a radioactive material, the half life of which is two days. After 32 days, the amount of radioactive material left in the sample is
|
(a) Less than 1 mg |
(b) |
(c) |
(d) 1 gm |
A parallel plate air capacitor is charged to a potential difference of V. After disconnecting the battery, distance between the plates of the capacitor is increased using an insulating handle. As a result, the potential difference between the plates
|
(a) Decreases |
(b) Increases |
(c) Becomes zero |
(d) Does not change |
The coil of dynamo is rotating in a magnetic field. The developed induced e.m.f. changes and the number of magnetic lines of force also changes. Which of the following condition is correct
|
(a) Lines of force minimum but induced e.m.f. is zero |
|
(b) Lines of force maximum but induced e.m.f. is zero |
|
(c) Lines of force maximum but induced e.m.f. is not zero |
|
(d) Lines of force maximum but induced e.m.f. is also maximum |
The electron in a hydrogen atom makes a transition
, where
and
are the principal quantum numbers of the two states. Assume the Bohr model to be valid. The time period of the electron in the initial state is eight times that in the final state. The possible values of n1 and n2 are
|
(a) |
(b) |
(c) |
(d) |
A radioactive sample of U238 decay to Pb through a process for which half life is 4.5 × 109 years. The ratio of number of nuclei of Pb to U238 after a time of 1.5 × 109 years (given 21/3 = 1.26)
|
(a) 0.12 |
(b) 0.26 |
(c) 1.2 |
(d) 0.37 |