List of top Questions asked in JEE Main

If wattless current flows in the AC circuit, then the circuit is:

In the circuit, the logical value of A = 1 or B = 1 when potential at A or B is 5 V and the logical value of A = 0 or B = 0 when potential at A or B is 0 V. The truth table of the given circuit will be:

 

In a series \(LR\) circuit \(X_L=R\) and power factor of the circuit is \(P_1\). When capacitor with capacitance C such that \(X_L=X_C\) is put in series, the power factor becomes \(P_2\). The ratio \(\frac {P_1}{P_2}\) is

An AC source is connected to an inductance of 100 mH, a capacitance of 100 μF and a resistance of 120 Ω as shown in the figure. The time in which the resistance having a thermal capacity 2 J/°C will get heated by 16°C is ___ s.
 

Fig. Circuit

A telegraph line of length 100km has a capacity of 0.01μF/km, and it carries an alternating current at 0.5kilo cycle per second. If the minimum impedance is required, then the value of the inductance that needs to be introduced in series is ______ mH.
(if π = √10)

A transformer operating at primary voltage 8 kV and secondary voltage 160 V serves a load of 80 kW. Assuming the transformer to be ideal with purely resistive load and working on unity power factor, the loads in the primary and secondary circuit would be

A series LCR circuit has
\(L = 0.01H, R = 10Ω\ and\ C = 1µF\)
and it is connected to ac voltage of amplitude (Vm)50 V. At frequency 60% lower than resonant frequency, the amplitude of current will be approximately

To light, a W, 100 V lamp is connected, in series with a capacitor of capacitance 
\(\frac{50}{π\sqrt{x}}\mu F\) with \(200 V\), 50 Hz AC source.
The value of x will be ___.

In the given circuit, the magnitude of VL and VC are twice that of VR. Given that f = 50 Hz, the inductance of the coil is 1/(Kπ) mH. The value of K is ________.

Fig.
Two metallic wires of identical dimensions are connected in series. If σ1 and σ2 are the conductivities of these wires, respectively, the effective conductivity of the combination is :
An alternating emf \(E = 440 \sin(100\pi t)\) is applied to a circuit containing an inductance of \(\frac{\sqrt{2}}{\pi}\) H. If an a.c. ammeter is connected in the circuit, its reading will be:
An alternating emf \(E = 440 \sin(100\pi t)\) is applied to a circuit containing an inductance of \(\frac{\sqrt{2}}{\pi}\) H. If an a.c. ammeter is connected in the circuit, its reading will be:
The current \(I\) flowing through the given circuit will be ________A.
current flowing through the circuit
The soft-iron is a suitable material for making an electromagnet. This is because soft-iron has

A resistance of 40 Ω is connected to a source of alternating current rated 220 V, 50 Hz. Find the time taken by the current to change from its maximum value to the rms value :

As shown in the figure an inductor of inductance 200 mH is connected to an AC source of emf 220 V and frequency 50 Hz. The instantaneous voltage of the source is 0 V when the peak value of current is\(\sqrt{\frac{a}{\pi}}\).The value of a is ___

The dimension of mutual inductance is :

Two coils of self-inductance L1 and L2 are connected in series combination having mutual inductance of the coils as M. The equivalent self-inductance of the combination will be:
Two coils of self-inductance L1 and L2 are connected in series combination having mutual inductance of the coils as M
A metallic conductor of length 1 m rotates in a vertical plane parallel to east-west direction about one of its end with angular velocity 5 rad s–1. If the horizontal component of earth’s magnetic field is 0.2 × 10–4 T, then emf induced between the two ends of the conductor is:
The magnetic moment of an electron (e) revolving in an orbit around nucleus with an orbital angular momentum is given by:
The current in a coil of self inductance \(2.0\ H\) is increasing according to \(I = 2\ sin(t^2)\ A\). The amount of energy spent during the period when current changes from 0 to \(2\ A\) is _______ \(J\).
Two concentric circular loops of radii \(r_1 = 30\) cm and \(r_2 = 50\) cm are placed in \(X–Y\) plane as shown in the figure. \(A\) current \(I = 7 \;A\) is flowing through them in the direction as shown in figure. The net magnetic moment of this system of two circular loops is approximately
Two concentric circular loops
A conducting circular loop is placed in X -Y plane in presence of magnetic field
\(\stackrel{→}{B} = (3t^3\hat{j}+3t^2\hat{k})\) in SI unit. If the radius of the loop is 1 m, the induced emf in the loop at time \(t = 2s\) is \(nπV\). The value of \(n\) is ______.
Two sources of equal emfs are connected in series. This combination is connected to an external resistance R. The internal resistances of the two sources are r1 and r2 (r1 > r2). If the potential difference across the source of internal resistance r1 is zero, then the value of R will be :

In a meter bridge experiment, for measuring unknown resistance ‘S’, the null point is obtained at a distance 30 cm from the left side as shown at point D. If R is 5.6 kΩ, then the value of unknown resistance ‘S’ will be ___Ω.

Fig. Meter Bridge