MCQ
The power loss is less in transmission lines, when:
- AVoltage is less but current is more
- BBoth voltage and current are more
- CVoltage is more but current is less
- DBoth voltage and current are less
Explanation:
The power cables have some resistance.
Power lost in the wires can be calculated as P = I2R with R as the resistance of the wires and I as the current that passes through them.
Power at the load is P = VI.
From this one can see that if voltage is increased by say n times, then only $\frac{1}{\text{n}}$ the current is required to deliver the same power. However, if $\frac{1}{\text{n}}$ current is passed
on the same wires, only $\frac{1}{\text{n}^2}$ of the power will be lost.
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In a nuclear fission reaction
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(a) Two light nuclei combine to produce a heavier nucleus |
|
(b) A light nucleus bombarded by thermal neutrons breaks up |
|
(c) A heavy nucleus bombarded by thermal neutrons breaks up |
|
(d) A heavy nucleus breaks up by itself |
A short magnet oscillates with a time period 0.1 s at a place where horizontal magnetic field is 24μT. A downward current of 18 A is established in a vertical wire 20 cm east of the magnet. The new time period of oscillator
|
(a) 0.1 s |
(b) 0.089 s |
(c) 0.076 s |
(d) 0.057 s |
The Lyman series of hydrogen spectrum lies in the region
|
(a) Infrared |
(b) Visible |
(c) Ultraviolet |
(d) Of X - rays |
An α particle and a proton travel with same velocity in a magnetic field perpendicular to the direction of their velocities, find the ratio of the radii of their circular path
|
(a) 4 : 1 |
(b) 1 : 4 |
(c) 2 : 1 |
(d) 1 : 2 |
In case of a real and inverted image, the magnification created by the mirror is:
The decay constant λ of the radioactive sample is the probability of decay of an atom in unit time, then
|
(a) λ decreases as atoms become older |
|
(b) λ increases as the age of atoms increases |
|
(c) λ is independent of the age |
|
(d) Behaviour of λ with time depends on the nature of the activity |