The figure shows a network of resistances in which the point $A$ is earthed. The current through the $4\,\Omega$ resistor is
Diffcult
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In the given figure $R_1=10 \Omega, R_2=8 \Omega, R_3=4 \Omega$ and $R_4=8 \Omega$. Battery is ideal with emf $12 \mathrm{~V}$. Equivalent resistant of the circuit and current supplied by battery are respectively.
Eels are able to generate current with biological cells called electroplaques. The electroplaques in an eel are arranged in $100$ rows, each row stretching horizontally along the body of the fish containing $5000$ electroplaques. The arrangement is suggestively shown below. Each electroplaques has an emf of $0.15\, V$ and internal resistance of $0.25 \,\Omega$ The water surrounding the eel completes a circuit between the head and its tail. If the water surrounding it has a resistance of $500 \,\Omega$, the current an eel can produce in water is about .............. $A$
A material '$B$' has twice the specific resistance of '$A$'. A circular wire made of '$B$' has twice the diameter ofa wire made of '$A$'. then for the two wires to have the same resistance, the ratio $\frac{{{l_B}}}{{{l_A}}}$ of their respective lengths must be
Four wires of the same diameter are connected in turn between two points, maintained at a constant potential difference. Their resistivities are; $\rho $ and $L$ (wire $1$ )., $1.2\,\rho $ and $1.2\,L$ (wire $2$ ), $0.9\,\rho $ and $0.9\,L$ (wire $3$ ) and $\rho $ and $1.5\,L$ (wire $4$ ). Rank the wires according to the rates at which energy is dissipated as heat, greatest first
Two batteries, one of $emf$ $18\, volts$ and internal resistance $2\,\Omega $ and the other of $emf$ $12\, volt$ and internal resistance $1\,\Omega $, are connected as shown. The voltmeter $V$ will record a reading of .............. $\mathrm{volt}$
Forty electric bulbs are connected in series across a $220\, V$ supply. After one bulb is fused, the remaining $39$ are connected again in series across the same supply. The illumination will be
A cable of resistance $10\,\Omega $ carries electric power from a generator producing $250\, kW$ at $10000\, volt$. The current in the cable is ............. $A$
Two wires $A$ and $B$ of the same material, having radii in the ratio $1: 2$ carry currents in the ratio $4: 1$. The ratio of drift speed of electrons in $A$ and $B$ is .......