Current Electricity-07 PROBLEMS

PROBLEMS 1. A thin uniform wire AB of length 1 m, an unknown resistance X and a resistance of 12 Ω are connected by thick conducting strips, as shown in the figure. A battery and a galvanometer (with a sliding jockey connected to it) are also available. Connections are to be made to measure the un- known resistance X using the principle of Wheatstone bridge. Answer the following questions: (a) Are there positive and negative terminals on the galvanometer ? (b) Copy the figure in your answer book and show the battery and the galvanometer (with jockey) connected at appropriate points. (c) After appropriate connections are made it is found that no deflection takes place in the galva- nometer when the sliding jockey touches the wire at a distance of 60 cm from A. Obtain the value of the resistance X. A B C D 2. Two capacitors A and B with capacities 3 μF and 2 μF are charged to a potential difference of 100V and 180V respectively. The plates of the capacitors are connected as shown in the figure with one wire of each capacitor free. The upper plate of A is positive and that of B is negative. An uncharged 2 μF capacitor C with lead wired falls on the free ends to complete the circuit. Calculate: 2F C + 3F A - 2F B (i) The final charge on the three capacitor, and (ii) the amount of electrostatic energy stored in the system before and the completion of the circuit. 3. An electrical circuit is shown in figure. Calculate the potential difference across the resistor of 400 ohm as will be measured by the voltmeter V of resistance 400 ohm either by applying Kirchoff’s rules or otherwise. l2 10 V

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