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Practice Online Test Series for JEE Main 2018 & NEET 2018
Magnetic field due to semi infinity length wire at point P:
A current of 1.6 A is flowing through a wire having cross-sectional area `1 mm^2`. If density of free electrons in the material of the wire is `10^29` per `m^3`, the drift velocity of electrons will be:
If the charge on a capacitor is increased by 2 C the energy stored in it increase by 21%. The original charge on the capacitor (in coulomb) is:
A charge q is placed in the middle of a line joining the two equal and like point charge Q. This charge q will remain in equilibrium for which value of q is:
A body of mass m is kept at a small height h above the ground. If the radius of the earth is R and its mass is M, the potential energy of the body and earth system (with `h=oo` being the reference position) is:
A negative test charge is moving near a long straight wire carrying a current. The force acting on the test charge is parallel to the direction of the current. The motion of the charge is
The current through a wire depends on time as `i=(2+3t)` mA. The charge crossing through a section of the wire in 1 min is:
A parallel plate capacitor with air between the plates has a capacitance of 9 pF. The separation between its plates is 'd'. The space between the plates is now filled with two dielectrics. One of the dielectrics has dielectric constant `K_1=3` and thickness `d/3` while the other one has dielectric constant `K_2=6` and thickness `(2d)/3`. Capacitance of the capacitor is now:
Two free positive charges 4q and q are a distance `l` apart. What charge Q is needed to achieve equilibrium for the entire system and where should it be placed form charge q?
A satellite moving round the earth in a circular orbit of radius r and speed v suddenly loses some of its energy. Then:
A coil of 50 turns and 4 cm radius carries 2A current then magnetic field at its center is:
Two electrical bulbs marked 40 W, 220 V and 60W, 220 V when connected in series across same voltage supply of 220 V, the effective power is `P_1` and when connected in parallel, the effective power is `P_2`. Then `(P_1/P_2)` is:
In which of the following stores maximum energy?
Four chargers are arranged at the corners of a square ABCD, as shown. The force on a +ve charge kept at the center of the square is
If the acceleration due to gravity at earth is g and mass of earth is 80 times that of moon and radius of earth is 4 times that of moon, the value of acceleration due to gravity at the surface of moon will be:
A proton moves on circular path with its constant angular speed then correct relation between its magnetic moment and angular momentum:
32 cells, each of emf 3V, are connected in series and kept in a box. Externally the combination shows an emf of 84 V. The number of cells reversed in the combination is:
The potential of the point A is greater than that of B by 19 volt. What is the potential difference in volts across the `3muF` capacitor?
The electric potential (V) as a function of distance (x) is given by `V=(5X^2+10X-9)` volt. The value of electric field at x=1 m would be-
In order to shift a body of mass m from a circular orbit of radius 3R to a higher radius 5R around the earth, the work done is:
