NEET Physics Current Electricity MCQs

A variable resistor $R$ is connected across a battery of emf $E$ and internal resistance $r$. For what value of $R$ is the power delivered to $R$ maximum?

A metallic conductor has a current of 5A flowing through it. The free electron density is $8.5 imes 10^{28} m^{-3}$. The cross-sectional area of the conductor is $2 imes 10^{-6} m^2$. If the average relaxation time is $2 imes 10^{-14} s$ and the electric field strength inside the conductor is 2 V/m, what is the mass of an electron (approximately)? (Assume the charge of an electron is $1.6 imes 10^{-19} C$).

A Wheatstone bridge is balanced when the galvanometer shows zero deflection. If a known resistance $R_1$ is doubled and the unknown resistance $R_x$ is halved, while keeping $R_2$ and $R_3$ constant, which of the following operations will rebalance the bridge?

In a meter bridge experiment, null point is obtained at $l$ cm from the left end. If a resistance $X$ is connected in series with the unknown resistance $R$, the null point shifts to $l'$ cm. What is the value of $R$?

A potentiometer wire of length 100 cm has a resistance of 10 Ω. It is connected in series with a resistance box and a 2V cell of negligible internal resistance. If a cell of emf $E_1$ is balanced against a length of 40 cm and another cell of emf $E_2$ is balanced against a length of 60 cm when the resistance in the box is 10 Ω and 5 Ω respectively, the ratio $\frac{E_1}{E_2}$ is:

A potentiometer wire AB is 100 cm long and has a total resistance of 10Ω. It is connected to a driver cell of emf E and internal resistance r. When a cell of emf $E_1$ is balanced against a length of $l_1$, the current through the potentiometer wire is $i_1$. When the cell $E_1$ is shunted by a resistance of 10Ω and balanced against a length $l_2$, the current through the potentiometer wire is $i_2$. Which of the following is true?

A galvanometer with a resistance of $50 \Omega$ and a full-scale deflection current of $100 \mu A$ is to be converted into a voltmeter with a range of 0-5V. A resistance $R_x$ is connected in series with the galvanometer. Simultaneously, an identical galvanometer is converted into an ammeter of range 0-10mA by connecting a shunt resistance $R_s$ in parallel. What is the relationship between $R_x$ and $R_s$?

A potentiometer wire of length 100cm has a resistance of 10Ω. It is connected in series with a resistance R and a cell of emf 2V and negligible internal resistance. A source of emf 10mV is balanced against a length of 40cm of the potentiometer wire. What is the value of the resistance R?

A metre bridge setup uses a standard resistance of $10\Omega$. A resistance wire of unknown value and uniform cross-section is connected across the left gap. The null point is obtained at $60\,cm$ from the left end. If the radius of the unknown wire is doubled without changing its length or resistivity, the new null point will be at:

In a metre bridge experiment, the null point is found at $40\,cm$ from the left end. A $12\Omega$ resistor is connected in parallel with the unknown resistance and the null point shifts to $60\,cm$. What is the value of the unknown resistance?