Q4: - In the circuit shown in the figure the power supply voltage = 6 volts, the length of the wire AB= 100 cm. If the point is at 50 cm the galvanometer G reads a current of 0 A and If the point is at 40 cm the galvanometer G reads a current of 0.1 A what is the value of internal resistance r in (12) of the unknown battery. [4 points) € 6V 21 B w Q5: - The resistance of copper is 100.2 at 0°C then it increases linearly up to 100°c. At a temperature of -234.5°C the resistance of copper is almost zero as shown in the figure. Find the temperature coefficient of the resistance (a). [4 points) Triince in a 2345 Temperature 100 Torstw on Copper Metal

Internal resistance of the unknown battery in the circuit is '60 ohms'. The 'temperature coefficient of resistance' for copper is around '0.00103/°C'.

Explanation:

The first part of the question pertains to the unknown internal resistance 'r' in an electric circuit. This can be determined using Ohm's law. If the point on wire AB is halfway, the potential difference is zero and when it shifts to 40cm, the current increases. This means the resistance of battery (r) corresponds to this 10cm. As the voltage supplied by the external battery (6 volts) and the measured current (0.1A) are known, we can apply Ohm's law: V = IR , r = V/I = 6/0.1 = 60 ohms. Hence, the internal resistance of the unknown battery is 60 ohms.

The second part of the question deals with the temperature coefficient of resistance for copper. This coefficient (a) is defined as the change in resistance per degree change in temperature. It is calculated as a = ∆R/(R0∆T), where ∆R is the change in resistance, R0 is the original resistance and ∆T is the change in temperature. Given the resistance at two different temperatures, we can find it: a = ΔR / (R0ΔT)=(100.2-0)/(100.2*(100-(-234.5))) = 0.00103/°C.

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