CBSE physics
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What ate permanent magnets? Give one example.
Substances that can retain their magnetism for a long duration of time at room temperature are called permanent magnets. They have high retentivity and coercivity.
Eg: Steel, cobalt
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What is the geometrical shape of equipotential surfaces due to a single isolated charge?
The equipotential surface for an isolated charge is concentric circles. The distance between the shell decreases with increase in electric field.
A capacitor has been charged by a dc source. What are the magnitudes of conduction and displacement currents, when it is fully charged?
When capacitor is charged by a dc source,
Conduction current is equal to the displacement current.
i.e., 
Because, 
is maximum when, capacitor is fully charged.
A 10 V battery of negligible internal resistance is connected across a 200 V battery and a resistance of 38 
as shown in the figure. Find the value of the current in circuit. 
Since the cells are in opposition,
E net = E1 – E2 = (200-10) = 190 V
So, current in the circuit is given by, I = 
The emf of a cell is always greater than its terminal voltage. Why? Give reason.
V= E – I r;
The emf of a cell is greater than terminal voltage because there is some potential drop across the cell due to its small internal resistance.
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Mock Test Series
Mock Test Series