Superconductors are the materials that lose all its resistance at very low temperature = 0 K
Applications of Super conductor are used
a) In making very strong electromagnets
b) In producing veru high speed computers

a) in parallel, power dissipation \(\alpha\) 1/R 
Therefore 3\(\Omega \) wire will dissipate more power
b) In series, power dissipation \(\alpha\) R
Therefore 9\(\Omega \) wire will dissipate more power

In these type of questions, we have to look out the connections of different cells, if the opposite terminals of all the cells are connected, then they support each other, i.e. these individual emf's are added up. If the same terminals of the cells are connected, then the equivalent emf is obtained by taking the difference of emf's.
Net emf of combination = E₁ - 2E₁ + 5E₁ = 4E₁
Net resistance of current = r + 2 r + 3r + R = 6r + R
∴ Current, I = V/R (from Ohm's law)
\(I=\frac { 4{ E }_{ 1 } }{ 6r+R } \)

When the bulb is turned ON, the resistance of the filament is low, the current is high and a relatively large amount of power is delivered to the bulb.
As the filament warm up, its resistance increases and the current decreases. As a result, power delivered to bulb decreases.

(i) Heat produced in the circuit is directly proportional to the resistance if a constant current is flowing through a circuit, because H = I²Rt or H \(\propto\) R. It is so in series combination of resistors.
(ii) Heat produced in the circuit is inversely proportional to the resistance if a constant pot. diff. is applied across the circuit, because
\(H=\frac{V^2}{R}t \)
or \(H \propto \frac{1}{R}\)
It is so in parallel combination of resistors.

Let V be the emf of the d.c. source in volt. \(R \ \Omega\) be the resistance of each resistor.
In series, total resistance = R + R + R = 3 R
Power dissipated = \(\frac{V^2}{3R}=X \ \ or \ \ \frac{V^2}{R}=3X\)
In parallel, total resistance, R' is given by
\(\frac{1}{R'}=\frac{1}{R}+\frac{1}{R}+\frac{1}{R}=\frac{3}{R} \ or \ \ R'=R/3\)
Power dissipated = \(\frac{V^2}{R'}=\frac{V^2}{R/3}=\frac{3V^2}{R}\)
= 3 x 3 x = 9 

While measuring a very low resistance using meter bridge, all other resistances used should have low values in order to ensure sensitivity of the bridge. This requires the galvanometer should also be of very low resistance and a very sensitive. Then the end resistances and resistances of the connecting wires used in metre bridge becomes comparable with the resistance to be measured. This would introduce error in the result. Due to it, measurement will not be accurate.

Terminal potential difference of a cell is defined as the potential difference between the two electrodes of a cell in a closed circuit. The value of terminal potential difference of a cell is less than the emf of a cell, when current is drawn from the cell. The value of terminal potential difference of a cell becomes greater than the emf of the cell during charging of the cell, i.e., when the positive electrode of the cell is connected to positive terminal of battery charger and negative electrode of the cell is connected to negative terminal of battery charger.

When the motor starter of a car is operated, it draws more current from the battery for the operation of car. Therefore, the voltage across the light bulb is lowered, hence the light of a car is dimmed.

While taking a bath if we play with a switch of light, the water comes in between current wire and our body. Due to it, the current flows through water to our body. Due to it, the current flows through water to our body, resulting in a shock.

V = 200 V; Value of carbon resistance,
\(R=60 \times 10^4 \ \Omega\);
so current, \(I=\frac{V}{R}=\frac{200}{60 \times 10^4}=3.33\times 10^{-4}A.\)

For student A, the numbers attached to brown, green and orange are 1, 5 and 3. So the value of resistor is R_A = 15 x 10³ \(\Omega\) =\(15 \ k \Omega\).
For student B, the numbers attached to black, green and red are 0, 5 and 2 respectively. So the value of resistor is, R_B = 05 x 10² \(\Omega\) =\(500 \ k \Omega\).
Thus, student A picked up the correct resistor of \(15 \ k \Omega\).

For manganin, the temperature coefficient of resistance is very low. Due to it, the resistance of manganin wire remains almost unchanged with a change in temperature. The resistivity of manganin is high. Therefore, for making a standard resistance of the given value, the smaller length of wire is needed. It is due to these facts, the wire of manganin is used for making standard resistance coil. The coil is double folded on itself to avoid the inductive effect and it wound over the non-conducting frame in order to avoid the conductive effect and the leakage of current.

The cause of death is not heating due to the current passing through a person. Though he may receive burns if the currents are too large. The cause of death is the interference of the external currents with our highly sensitive nervous system which is basically electrical in nature, which in turn affects the heart beating. Beyond a certain point, this interference becomes fatal.

Mobility,  \(\mu = \frac{drift \ \ velocity}{electric \ \ field}=\frac{v_d}{E}\)
(a) The charge carriers in an electrolyte are positive and negative ions.
(b) The charge carriers in an ionised gas are electrons and positively charged ions.