JEE Current & Resistance PYQs With Video Solutions PDF

A galvanometer has a coil of resistance $$200\Omega$$ with a full scale deflection at $$20\mu A$$. The value of resistance to be added to use it as an ammeter of range $$(0 - 20)$$ mA is :

A $$6.0$$ volt battery is connected to two light bulbs as shown in figure. Light bulb 1 has resistance $$3$$ ohm while light bulb 2 has resistance $$6$$ ohm. Battery has negligible internal resistance. Which bulb will glow brighter?

The current flowing through a conductor connected across a source is $$2$$ A and $$1.2$$ A at $$0°$$C and $$100°$$C respectively. The current flowing through the conductor at $$50°$$C will be _____ $$\times 10^2$$ mA.

Two metallic wires of identical dimensions are connected in series. If $$\sigma_1$$ and $$\sigma_2$$ are the conductivities of these wires respectively, the effective conductivity of the combination is:

If the radius of earth is reduced to three-fourth of its present value without change in its mass then value of duration of the day of earth will be _________ hours 30 minutes.

A current of 5 A is passing through a non-linear magnesium wire of cross-section 0.04 m$$^2$$. At every point the direction of current density is at an angle of 60$$^\circ$$ with the unit vector of area of cross-section. The magnitude of electric field at every point of the conductor is: (resistivity of magnesium $$\rho = 44 \times 10^{-8}$$ $$\Omega$$m)

The $$H$$ amount of thermal energy is developed by a resistor in 10 s when a current of 4 A is passed through it. If the current is increased to 16 A, the thermal energy developed by the resistor in 10 s will be

In a large building, there are 15 bulbs of 40 W, 5 bulbs of 100 W, 5 fans of 80 W and 1 heater of 1 kW. The voltage of the electric mains is 220 V. The minimum capacity of the main fuse of the building will be:

The resistance of an electrical toaster has a temperature dependence given by $$R(T) = R_0[1 + \alpha(T - T_0)]$$ in its range of operation. At $$T_0 = 300$$ K, $$R = 100$$ $$\Omega$$ and at $$T = 500$$ K, $$R = 120$$ $$\Omega$$. The toaster is connected to a voltage source at 200 V and its temperature is raised at a constant rate from 300 to 500 K in 30 s. The total work done in raising the temperature is:
Note: This question was awarded as the bonus since all options were incorrect in the exam.

A constant voltage is applied between two ends of a metallic wire. If the length is halved and the radius of the wire is doubled, the rate of heat developed in the wire will be:

A metal wire of resistance 3 $$\Omega$$ is elongated to make a uniform wire of double its previous length. This new wire is now bent and the ends joined to make a circle. If two points on this circle make an angle 60° at the center, the equivalent resistance between these two points will be:

A uniform metallic wire has a resistance of 18 $$\Omega$$ and is bent into an equilateral triangle. Then, the resistance between any two vertices of the triangle 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?

Which of the following resistivity $$(\rho) v/s$$ temperature (T) curves is most suitable to be used in wire bound standard resistors?

By what percentage will the illumination of the lamp decrease if the current drops by 20%?

In a meter bridge experiment $$S$$ is a standard resistance. $$R$$ is a resistance wire. It is found that balancing length is $$l = 25$$ cm. If $$R$$ is replaced by a wire of half length and half diameter that of $$R$$ of same material, then the balancing distance $$l'$$ (in cm) will now be ___________.

In a conductor, if the number of conduction electrons per unit volume is $$8.5 \times 10^{28}$$ m$$^{-3}$$ and mean free time is 25 fs (femto second), it's approximate resistivity is: ($$m_e = 9.1 \times 10^{-31}$$ kg)

A uniform metallic wire carries a current 2 A, when 3.4 V battery is connected across it. The mass of uniform metallic wire is $$8.92 \times 10^{-3}$$ kg, density is $$8.92 \times 10^3$$ kg m$$^{-3}$$ and resistivity is $$1.7 \times 10^{-8}$$ $$\Omega$$ - m. The length of wire is:

Drift speed of electrons, when 1.5 A current flows in a copper wire of cross section 5 mm$$^2$$ is $$v_d$$. If the electron density in copper is $$9 \times 10^{28}$$ m$$^{-3}$$, the value of $$v_d$$ in mm s$$^{-1}$$ is close to (Take charge of an electron to be $$= 1.6 \times 10^{-19}$$ C)

Two equal resistances when connected in series to a battery, consume electric power of 60 W. If these resistance are now connected in parallel combination to the same battery, the electric power consumed will be:

Space between two concentric conducting spheres of radii a and b (b > a) is filled with a medium of resistivity $$\rho$$. The resistance between the two spheres will be:

Resistances are connected in a meter bridge circuit as shown in the figure. The balancing length $$l_1$$ is $$40 \text{ cm}$$. Now an unknown resistance $$x$$ is connected in series with $$P$$ and new balancing length is found to be $$80 \text{ cm}$$ measured from the same end. Then the value of $$x$$ will be ______ $$\Omega$$.( Value of Q = 6 $$\Omega$$)

In a building there are 15 bulbs of 45 W, 15 bulbs of 100 W, 15 small fans of 10 W and 2 heaters of 1 kW. The voltage of electric main supply is 220 V. The minimum fuse capacity (rated value) of the building will be:

In a balanced Wheatstone bridge network, the resistances in the four arms taken in cyclic order are $$P = 10\ \Omega$$, $$Q = 20\ \Omega$$, $$S = 40\ \Omega$$, and $$R = X\ \Omega$$. Find the value of the unknown resistance $$X$$ in ohms ($$\Omega$$).

If a copper wire is stretched to increase its length by 20%. The percentage increase in resistance of the wire is _____%.

Find the equivalent resistance between two ends of the following circuit

Four bulbs B$$_1$$, B$$_2$$, B$$_3$$ and B$$_4$$ of 100 W each are connected to 220 V main as shown in the figure. The reading in the ideal ammeter will be:

To find the resistance of a galvanometer by the half deflection method, the following circuit is used with resistances $$R_1 = 9970$$ $$\Omega$$, $$R_2 = 30$$ $$\Omega$$ and $$R_3 = 0$$. The deflection in the galvanometer is d. With $$R_3 = 107$$ $$\Omega$$, the deflection changed to $$\frac{d}{2}$$. The galvanometer resistance is approximately:

The Wheatstone bridge shown in the figure below, gets balanced when the carbon resistor used as $$R_1$$ has the colour code (orange, red, brown). The resistors $$R_2$$ and $$R_4$$ are 80 $$\Omega$$ and 40 $$\Omega$$, respectively. Assuming that the colour code for the carbon resistors gives their accurate values, the colour code for the carbon resistor, used as $$R_3$$, would be:

A 200 $$\Omega$$ resistor has certain colour code. If one replaced the red colour by green in the code, the new resistance will be: