always settles in the magnetic N-S direction.
is repelled by a magnet.
always settles in the magnetic E-W direction
is attracted by a magnet.
Correct answer is A
The conclusive test for magnetism in a steel bar suspended horizontally at its midpoint is when the bar always settles in the magnetic N-S (North-South) direction.
Which of the following devices is associated with alternating currents only?
Step-up transformer
Induction coil
Moving coil galvanometer
Lead-acid accumulator
Correct answer is A
The device associated with alternating currents (AC) only from the provided options is the step-up transformer. Step-up transformers are specifically designed to work with alternating currents and are used to increase voltage levels in AC systems.
Which part of the human eye performs the same function as the diaphragm in a lens camera?
Choroid
Retina
Iris
Cornea
Correct answer is C
The part of the human eye that performs a function similar to the diaphragm in a camera lens is the Iris.
Just like the diaphragm in a camera lens controls the amount of light entering the camera, the iris in the eye controls the amount of light that enters the eye by adjusting the size of the pupil. It can contract or expand to regulate the size of the pupil in response to varying light conditions, thus controlling the amount of light that reaches the retina at the back of the eye.
The purpose of commutators in a direct current motor is to
reverse the direction of the current after every half rotation
increase the number of rotations per second
enable a uniform couple to act on the coil.
increase the efficiency of the motor.
Correct answer is A
The purpose of commutators in a direct current (DC) motor is to reverse the direction of the current after every half rotation.
When an electron jumps directly from an orbit of n = 4 to n = 2,
a photon is absorbed
a photon is emitted
two photons are emitted.
two photons are absorbed
Correct answer is B
When an electron jumps directly from an orbit of n = 4 to n = 2, a photon is emitted.
This is a typical scenario in atomic physics where an electron transitions from a higher energy level (orbit) to a lower energy level. During this transition, the electron loses energy, and this energy is emitted in the form of a photon. The energy of the emitted photon corresponds to the energy difference between the two energy levels, as described by the quantization of energy levels in the Bohr model of the atom.
What is the name given to the force of attraction between the nucleons in the nucleus of an atom?
Gravitational force.
Electrostatic force.
Magnetic force.
Nuclear force.
Correct answer is D
The force of attraction between the nucleons (protons and neutrons) in the nucleus of an atom is called the nuclear force or strong nuclear force. This force is responsible for holding the protons and neutrons together in the nucleus despite the electrostatic repulsion between positively charged protons. It is one of the fundamental forces in nature and plays a crucial role in the stability of atomic nuclei.
is positively charged and is concentrated in a tiny volume
contains protons and electrons distributed in a tiny volume.
is concentrated in a tiny volume and contains alpha particles.
is distributed in a tiny volume and emits alpha particles.
Correct answer is A
The Rutherford scattering experiment showed that the nucleus of an atom:
is concentrated in a tiny volume and is positively charged.
In the experiment, when alpha particles were fired at a thin gold foil, most of the alpha particles passed straight through, but a few were deflected considerably. This result led Rutherford to conclude that the positive charge of the atom is concentrated in a small, dense nucleus at the center of the atom. The fact that some alpha particles were deflected strongly indicated that there was a positively charged nucleus within the atom. This experiment was crucial in developing our understanding of atomic structure and led to the model of the atom with a central nucleus containing protons and neutrons, surrounded by electrons.
150J
200J
50J
100J
Correct answer is C
\(M_{bullet}\) = 0.05kg, \(V_{bullet}\) = 200m/s, \(M_{block}\) = 0.95kg and \(V_{block}\) = 0
for an inelastic collision
\(M_{bullet} \times V_{bullet} + M_{block} \times V_{block} = (M_{bullet} + M_{block})\)v
0.05 x 200 + 0.95 x 0 = ( 0.05 + 0.95)v
10 + 0 = v
v = 10m/s
K.E of the block = \(\frac{1}{2}mv^2\)
K . E = \(\frac{1}{2} \times(0.05 + 0.95) \times10^2\) ( bullet now part of the block)
K . E = \(\frac{1}{2} \times1 \times100\)
= 50J
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