A uniform wire of diameter $$d$$ carries a current of $$100 \mathrm{~mA}$$ when the mean drift velocity of electrons in the wire is $$v$$. For a wire of diameter $$\frac{d}{2}$$ of the same material to carry a current of $$200 \mathrm{~mA}$$, the mean drift velocity of electrons in the wire is
In an electrical circuit, the voltage is measured as $$V=(200 \pm 4)$$ volt and the current is measured as $$I=(20 \pm 0.2)$$ A. The value of the resistance is:
A step up transformer is connected to an ac mains supply of $$220 \mathrm{~V}$$ to operate at $$11000 \mathrm{~V}, 88$$ watt. The current in the secondary circuit, ignoring the power loss in the transformer, is
A particle is moving along $$x$$-axis with its position (x) varying with time $$(t)$$ as $$x=\alpha t^4+\beta t^2+\gamma t+\delta$$. The ratio of its initial velocity to its initial acceleration, respectively, is: