Which type of material must be used for lightning rod?
Lightning rods are made from the metal rod that are attached to the roof of a building. It was first... View Article
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Intensity of magneticfield due to earth at a point inside a hollow steel box is
No magnetic lines of force passes through the steel box.
Change in speed would continue as long as an unbalanced force is applied
Unbalanced forces acting on an object brings it in motion. The direction of motion is along the direction of greater... View Article
Richter scale is used to?
The power of an earthquake is expressed in terms of magnitude on a scale called Richter scale.
By a monochromatic wave, we mean[AFMC 1995]
Monochromatic wave means of single wavelength not thesingle colour
How does electric discharge in lightning occurs if air is a bad conductor?
When the magnitude of the accumulated charges becomes very large, the air which is normally a poor conductor of electricity,... View Article
Choose the best option about lightning:
Lightning occurs as a result of the flow of charge from clouds to the ground i.e. It happens through the... View Article
How to calculate the energy of a photon?
The energy of a photon is calculated in two ways as follows: If the frequency f of the photon is... View Article
A particle which has zero rest mass and non-zero energy and momentum must travel with a speed
Particle is photon and it travels with the velocity equal to light in vacuum m0 = 0 \(\begin{array}{l}m=\frac{m_{0}}{\sqrt{1-\frac{v^{2}}{c^{2}}}}\end{array} \) \(\begin{array}{l}1-\frac{v^{2}}{c^{2}}=0\end{array} \)... View Article
Which of the following decreases in motion along a straight line with constant retardation while the body is moving away from the origin?
a) Speed b) Acceleration c) Displacement d) None of the above When a body moves along a straight line with... View Article
In Millikan’s experiment for thedetermination of the charge on the electron, the reason for using the oil is
In Millikan’s experiment, drops of non-volatile liquid (cloak oil) are used to prevent evaporation.
Due to internal combustion inside a rocket, gases are ejected at the rate of 2.4 kg/minute. The velocity of the gases with respect to the rocket is 400 m/s. Calculate force exerted on the rocket
Rate of change of mass = (dm/dt) = 2.4kg/minute = (2.4/60) kg/sec = 0.04 kg/sec Force= Rate of change of... View Article
What do you see if you look at the clouds closely with electroscope ? 1. Upper parts of the clouds are positively charged. 2. Cloud is electrically neutral (no charge) everywhere. 3. Upper parts of clouds are negatively charged. 4. Lower parts of clouds are negatively charged.
In clouds, the upper parts are usually positively charged and the lower parts are usually negatively charged.
The coordination number of Cu is [AMU 1992]
Cu has fcc structure, for fccstructure co-ordination number = 12
When 2 charged glass rods, after being rubbed with silk cloths, are brought towards each other, they
Glass rods acquire positive charges. When these rods possessing like charges are brought towards each other, they repel each other.
A bullet of mass 0.02 kg is fired from a rifle. The bullet takes 0.02s to move through the barrel and leaves with a velocity of 200 ms–1. What is the acceleration acting on the bullet?
Initial velocity of the bullet = 0 ms-1 Final velocity of the bullet = 200 ms-1 Time to travel =... View Article
In anamplitude modulated wave for audio frequency of 500 cycle/second, the appropriate carrier frequency will be [AMU 1996]
Carrier frequency > audio frequency
The charge which is acquired by the glass rod when rubbed with a piece of silk is?
It is a convention to consider the charge acquired by a glass rod when it is rubbed with silk as... View Article
Statement 1: The flow of current in a poor conductor is impossible. Statement 2: Under certain conditions current flows through a poor conductor.
Poor conductors are those, which do not allow electricity to flow through them easily, but under certain conditions we can... View Article
Which one of the series of hydrogen spectrum is in the visible region [RPMT1999;MP PET 1990; MP PMT 1994;AFMC 1998; CBSE PMT 1990; MH CET 2004]
Balmer series lies in the visible region
