For comparing the $e.m.f.$'s of two cells with a potentiometer, a standard cell is used to develop a potential gradient along the wires. Which of the following possibilities would make the experiment unsuccessful
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(d) The emf of the standard cell must be greater than that of experimental cells, otherwise balance point is not obtained.
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In $a$ wire of cross-section radius $r$, free electrons travel with drift velocity $v$ when a current $I$ flows through the wire. What is the current in another wire of half the radius and of the same material when the drift velocity is $2v$?
The resistance of platinum wire at $0^{\circ}\,C$ is $2\,\Omega$ and $6.8\,\Omega$ at $80^{\circ} \,C$. The temperature coefficient of resistance of the wire is :
A horizontal conductor is oriented north south and carries some current. $A$ positively charged particle located vertically above it and having a velocity directed north ward experiences an upward force.What is the direction of the force if this charged particle were located to the east of the conductor and had a velocity directed towards the conductor
A resistance of $4\,\Omega $ and a wire of length $5\,m$ and resistance $5\,\Omega $ are joined in series and connected to a cell of $e.m.f.$ $10\, V$ and internal resistance $1\,\Omega $. A parallel combination of two identical cells is balanced across $300\, cm$ of the wire. The $e.m.f.$ $E$ of each cell is ........... $V$
If resistance of voltmeter is $10000 \,\Omega$ and resistance of ammeter is $2 \,\Omega$ then find $R$ when voltmeter reads $12\,V$ and ammeter reads $0.1\, A$ ............... $\Omega$
The potential difference across the $100\,\Omega$ resistance in the following circuit is measured by a voltmeter of $900 \,\Omega$ resistance. The percentage error made in reading the potential difference is
An electric bulb rated for $500\, watts$ at $100\, volts$ is used in a circuit having a $200-volt$ supply. The resistance $R$ that must be put in series with the bulb, so that the bulb draws $500\, W$ is .................. $\Omega$
The heating coils rating at $220\, volt$ and producing $50\, cal/sec$ heat are available with the resistances $55\,\Omega $ , $110\,\Omega$ , $220\,\Omega $ and $440\,\Omega $. The heater of maximum power will be of............. $\Omega$
Two solid conductors are made up of same material, have same length and same resistance. One of them has a circular cross section of area $A_{1}$ and the other one has a square cross section of area $A_{2}$. The ratio $\frac{A _{1}}{A _{2}}$ is