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Define one ampere.
The resistance of a wire of 0·01 cm radius is 14 Ω. If the resistivity of the material of the wire is 44 × 10⁻⁸ Ωm, find the length of the wire. (Given π = 22/7)
The filament of an electric lamp draws a current of 0·5 A, which lights for 2 hours. Calculate the charge that flows through the circuit.
An electric source can supply a charge of 750 coulomb. If the current drawn by a device is 15 mA, find the time in which the electric source will be discharged completely.
The potential difference across the two ends of a circuit component is decreased to one-third of its initial value, while its resistance remains constant. What change will be observed in the current flowing through it? Name and state the law which helps us to answer this question.
Draw a schematic diagram of a circuit consisting of a battery of four 1·5 V cells, a 5 Ω resistor, a 10 Ω resistor and a 15 Ω resistor and a plug key, all connected in series. Now find (I) the electric current passing through the circuit, and (II) potential difference across the 10 Ω resistor when the plug key is closed.
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