Two square metal plates $A$ and $B$ are of the same thickness and material. The side of $B$ is twice that of $A$. These are connected as shown in series. If the resistances of $A$ and $B$ are denoted by $R_A$ and $R_B,$ then $(R_A/R_B)$ is
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A battery is connected to a uniform resistance wire $AB$ and $B$ is earthed. Which one of the graphs below shows how the current density $J$ varies along $AB$
A uniform heating wire of resistance $36\, \Omega$ is connected across a potential difference of $240\, {V}$ The wire is then cut into half and potential difference of $240\, {V}$ is applied across each half separately. The ratio of power dissipation in first case to the total power dissipation in the second case would be $1: {x}$, where ${x}$ is........... .
A resistance of $2 \Omega$ is comnected across one gap of a metre-bridge (the length of the wire is $100 \mathrm{~cm}$ ) and an unknown resistance, greater than $2 \Omega$, is connected across the other gap. When these resistance are interchanged, the balance point shifts by $20 \mathrm{~cm}$. Neglecting any corrections, the unknown resistance is
The current in the primary circuit of a potentiometer is $0.2\, A$. The specific resistance and cross section of the potentiometer wire are $4\times10^{-7}\,ohm$ $metre$ and $8\times10^{-7}\, m^2$ respectively. The potential gradient will be equal to .............. $V/m$
Some electric bulbs are connected in series across a $220\, V$ supply in a room. If one bulb is fused then remaining bulbs are connected again in series across the same supply. The illumination in the room will
If $n,\,e,\,\tau $ and $m$ respectively represent the density, charge relaxation time and mass of the electron, then the resistance of a wire of length $l$ and area of cross-section $A$ will be
The current in a conductor varies with time t as $I = 2t + 3{t^2}$ where $I$ is in ampere and $t$ in seconds. Electric charge flowing through a section of the conductor during $t = 2\,\sec$ to $t = 3\,\sec$ is ............. $C$