Two wires that are made up of two different materials whose specific resistance are in the ratio $2 : 3$, length $3 : 4$ and area $4 : 5$. The ratio of their resistances is
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Two cells of emf $E_1$ and $E_2\left(E_1 > E_2\right)$ are connected individually to a potentiometer and their corresponding balancing length are $625 \,cm$ and $500 \,cm$, then the ratio $\frac{E_1}{E_2}$ is ...........
A copper rod of cross-sectional area $A$ carries a uniform current $I$ through it. At temperature $T$, if the volume charge density of the rod is $\rho $, how long will the charges take to travel a distance $d$ ?
A $100\, W \, bulb\, B_1$ and two $60\, W \,bulbs \,B_2$ and $B_3$, are connected to a $220\, V$ source, as shown in Figure. Now $P_1, P_2$ and $P_3$ are the output powers of the bulbs $B_1, B_2$ and $B_3$ respectively. Then
The charge flowing in a conductor varies with time as $Q = at -bt^2$. Then for current, which statement is incorrect.
$(A)$ decreases linearly with time
$(B)$ reaches a maximum and then decreases
$(C)$ fall to zero after time $t = a/2b$
$(D)$ changes at a rate $-2b$
Options :
In a hydrogen discharge tube it is observed that through a given cross-section $3.13 \times {10^{15}}$ electrons are moving from right to left and $3.12 \times {10^{15}}$ protons are moving from left to right. What is the electric current in the discharge tube and what is its direction
Resistances of $6\, ohm$ each are connected in the manner shown in adjoining figure. With the current $0.5\,ampere$ as shown in figure, the potential difference ${V_P} - {V_Q}$ is .............. $V$
A wire when connected to $220\,V$ mains supply has power dissipation ${P_1}$. Now the wire is cut into two equal pieces which are connected in parallel to the same supply. Power dissipation in this case is ${P_2}$. Then ${P_2}:{P_1}$ is