List of practice Questions

Silver has a work function of 4.7 eV. When ultraviolet light of wavelength 100 nm is incident on it, a potential of 7.7 V is required to stop the photoelectrons from reaching the collector plate. How much potential will be required to stop photoelectrons when light of wavelength 200 nm is incident on it?
If the distance of 100 W lamp is increased from a photocell, the saturation current in the photocell varies with the distance \( d \) as?
Following process is known as?
During charging a capacitor, variations of potential \( V \) of the capacitor with time \( t \) is shown as?
When a resistor of 11 Ω is connected in series with an electric cell, the current following in it is 0.5 A. Instead, when a resistor of 5Ω is connected to the same electric cell in series, the current increases by 0.4 A. The internal resistance of the cell is?
A battery is charged at a potential of 15 V in 8 h when the current flowing is 10 A. The battery on discharge supplies a current of 5 A for 15 h. The mean terminal voltage during discharge is 14V. The watt-hour efficiency of the battery is?
Which has more luminous efficiency?
The resistance of a germanium junction diode whose \( V-I \) is shown in figure is ( \( V_k = 0.3 \, V \))?
In hydrogen discharge tube, it is observed that through a given cross-section \( 3.31 \times 10^{15} \) electrons are moving from right to left and \( 3.12 \times 10^{8} \) protons are moving from left to right. The current in the discharge tube and its direction will be?
In a semiconductor, separation between conduction and valence band is of the order of?
If 1000 droplets each of potential 1 V and radius \( r \) are mixed to form a big drop, then the potential of the drop as compared to small droplets will be?
A Zener diode, having breakdown voltage equal to 15 V, is used in a voltage regulator circuit shown in figure. The current through the diode is?
The activity of a radioactive sample is measured as \( N_0 \) counts per minute at \( t = 0 \) and \( N \) counts per minute at \( t = 5 \) min. The time, in minutes, at which the activity reduces to half its value is?
The output Y of the logic circuit shown in figure is best represented as?
A resistor of 6kΩ with tolerance 10% and another resistance of 4kΩ with tolerance 10% are connected in series. The tolerance of the combination is about?
If we add impurity to a metal, those atoms also deflect electrons. Therefore?
A proton and an α-particle, accelerated through the same potential difference, enter a region of uniform magnetic field normally. If the radius of the proton orbit is 10 cm, then the radius of α-particles is?
An ammeter and a voltmeter of resistance \( R \) are connected in series to an electric cell of negligible internal resistance. Their readings are A and V respectively. If another resistance \( R' \) is connected in parallel with the voltmeter, then?
A neutron is moving with velocity \( v \). It collides head on and elastically with an atom of mass number \( A \). If the initial kinetic energy of the neutron is \( E \), then how much kinetic energy will be retained by the neutron after reflection?
If a magnet is suspended at angle 30° to the magnet meridian, the dip of needle makes angle of 45° with the horizontal, the real dip is?
An electron moves at right angle to a magnetic field of \( 5 \times 10^{-2} \, T \) with a speed of \( 6 \times 10^{7} \, \text{m/s} \). If the specific charge of the electron is \( 1.7 \times 10^{11} \, \text{C/kg} \), the radius of the circular path will be?
A solenoid 30 cm long is made by winding 2000 loops of wire on an iron rod whose cross-section is \( 1.5 \, \text{cm}^2 \). If the relative permeability of the iron is 6000, what is the self-inductance of the solenoid?
A coil of resistance 10 Ω and an inductance 5 H is connected to a 100 V battery. The energy stored in the coil is?
A galvanometer has current range of 15 mA and voltage range 750 mV. To convert this galvanometer into an ammeter of range 25 A, the required shunt is?
The denial cell is balanced on 125 cm length of a potentiometer. Now, the cell is short-circuited by a resistance of 2Ω and the balance is obtained at 100 cm. The internal resistance of the denial cell is?