Current electricity practice · Medium

The charge flowing in a conductor changes with time as $Q(t)=\alpha t-\beta t^2+\gamma t^3$. Where $\alpha, \beta$ and $\gamma$ are constants. Minimum value of current is

The potentiometer is superior to a voltmeter for measuring a potential difference because

If the free electron density be n and relaxation time be $\tau$, the electrical conductivity of a conductor may be expressed as

A parallel-plate capacitor of plate area $40 \mathrm{~cm}^2$ and separation between the plates $0.10 \mathrm{~mm}$ is connected to a battery of emf $2.0 \mathrm{~V}$ through a $16 \Omega$ resistor. Find the electric field in the capacitor $10 \mathrm{~ns}$ after the connections are made.

In the process of electrolysis the current is carried out inside the electrolyte by

With the rise of temperature the resistivity of a semiconductor

Three resistance $P,\,\,Q,\,\,R$ each of $2\,\,\mathrm{\Omega }$ and an unknown resistance S form the four arms of a wheatstone bridge circuit. When a resistance of $6\,\,\mathrm{\Omega }$ is connected in parallel to $S$ the bridge gets balanced. What is the value of $S$

A $25W,220V$ bulb and a $100W,220V$ bulb are connected in series across $440V$ line

Assertion: Electric field outside the conducting wire which carries a constant current is zero.

Reason: Net charge on conducting wire is zero.

Assertion: Electric field due to steady current carrying wire is zero outside the wire.
Reason: Net charge present in a current carrying wire is zero.

The equivalent resistance of resistor connected in series is always

Current passing through 2 conductors A and B varies with applied potential difference across their edge as shown. Compare their resistances $R_A$ and $R_B$.

Pick out the wrong statement

Assertion: When current through a bulb is increased by $2 \%$ power increase by $4 \%$

Reason: Current passing through the bulb is $\propto \frac{1}{\text { Resistance }}$

A current of $\mathrm{0}\mathrm{.01}\,\,\mathrm{mA}$ passes through the potentiometer wire of a resistivity of
${10^9}\,\,\,\,\Omega - \mathrm{cm}$ and area of cross-section ${10^{ - 2}}\,\,\mathrm{c}{\mathrm{m}^2}$. The potential gradient is

The electrical resistance of mercury column in a cyclindrical container is "$R$". The mercury is poured into another cylindrical container with half the radius of cross section. The resistance of the mercury column is

The two bulbs, one of $\mathrm{60}\,\,\mathrm{W}$ and other $\mathrm{200}\,\,\mathrm{W}$ are connected in series to a $\mathrm{200 \,\,volt}$ line, then

The current inside a copper voltameter

A dry cell of emf $1.6 \mathrm{~V}$ and internal resistance $0.10 ~\Omega$ is connected to a resistance of $R$ ohm. The current drawn from the cell is $2.0 \mathrm{~A}$. Find the voltage drop across $R$.

The material used for electric fuse is an alloy of tin and lead. This alloy should have:

A wire has a non-uniform cross-sectional area as shown in figure. A steady current $i$ flows through it. Which one of the following statement is correct

Which factor is immaterial for the wire used in electric fuse?

Constantine wire is used in making standard resistances because its

What is total resistance of wire?

The material of wire of potentiometer is

Assertion: Electric field inside a current carrying wire is zero.
Reason: Net charge in a current carrying wire is non zero.

The temperature at which thermal electric power of a thermo couple becomes zero is called

Fractional increase in resistivity per unit increase in temperature is defined as

When two identical batteries of internal resistance $1\,\,\mathrm{\Omega }$ each are connected in series across a resistor $R$, the rate of heat produced in $R$ is ${J_1}$. When the same batteries are connected $\mathrm{I}$ parallel across $R$, the rate is ${J_2}$. If ${J_1} = 2.25\,\,{J_2}$ then the value of $R$ in $\mathrm{\Omega }$ is

If an electron revolves in the path of a circle of radius of $0.5 \times 10^{-10} {~m}$ at a frequency of $5 \times 10^{15}$ cycle/sec. The electric current in the circle is:
(Charge of an electron is $1.6 \times 10^{-19} {C}$ )