Physics

At a certain location in Africa, a compass points 12^{\circ} west of the geographic north. The north tip of the magnetic needle of a dip circle placed in the plane of magnetic meridian points above the horizontal. The horizontal component of the earth’s field is measured to be 0.16 \mathrm{G} . Specify the direction and magnitude of the earth’s field at the location.At a certain location in Africa, a compass points 12^{\circ} west of the geographic north. The north tip of the magnetic needle of a dip circle placed in the plane of magnetic meridian points above the horizontal. The horizontal component of the earth’s field is measured to be 0.16 \mathrm{G} . Specify the direction and magnitude of the earth’s field at the location.

Ans: In the above question it is given that: Angle of declination, $\theta=12^{\circ}$ Angle of dip, $\delta=60^{\circ}$ Horizontal component of earth's magnetic field, $B_{H}=0.16 \mathrm{G}$...

read more

Two wires of equal lengths are bent in the form of two loops. One of the loops is square shaped whereas the other loop is circular. These are suspended in a uniform magnetic field and the same current is passed through them. Which loop will experience greater torque? Give reasons.

Ans: We know the expression for torque as, $$ \begin{array}{l} \tau=\mathrm{NIAB} \\ \Rightarrow \tau \propto \mathrm{A} \end{array} $$ Since, we know that the area of circular loops is more than...

read more

In a Van de Graaff type generator a spherical metal shell is to be a 15 \times 10^{6} \vee electrode. The dielectric strength of the gas surrounding the electrode is 5 \times 10^{7} \mathrm{Vm}^{-1}. What is the minimum radius of the spherical shell required? (You will learn from this exercise why one cannot build an electrostatic generator using a very small shell which requires a small charge to acquire a high potential.)

Ans: Given that, Potential difference is given as, $V=15 \times 10^{6} \mathrm{~V}$ Dielectric strength of the surrounding gas $=5 \times 10^{\top} \mathrm{Vm}^{-1}$ Electric field intensity is...

read more

When a glass rod is rubbed with a silk cloth, charges appear on both. A similar phenomenon is observed with many other pairs of bodies. Explain how this observation is consistent with the law of conservation of charge. Ans: Rubbing is a phenomenon in which there is production of charges equal in

Ans: Since unlike charges attract and like charges repel each other, the particles 1 and 2 moving towards the positively charged plate are negatively charged whereas the particle 3 that moves...

read more

A parallel-plate air condenser of plate area A and separation d is charged to potential V and then the battery is removed. Now a slab of dielectric constant k is introduced between the plates. If Q, E, and W denote respectively the magnitude of the charge on each plate, the electric field between the plates (after the introduction of the dielectric slab) and work done on the system in the process of introducing the slab, then
A \quad W=\frac{\xi_{10} \mathrm{~A} \mathrm{~V} \mathrm{~h}^{2}}{2 \mathrm{~d}}(1-1 / \mathrm{k})
B \quad Q=\frac{\xi_{1} K_{A} V}{d}
c \quad Q=\frac{\xi_{11} \mathrm{~A} \mathrm{~V}}{\mathrm{~d}}
\mathrm{D} \quad \mathrm{E}=\frac{\mathrm{V}}{\mathrm{kd}}

Correct option is A $\mathrm{W}=\frac{\varepsilon_{0} \mathrm{~A} \mathrm{~V} \mathrm{~h}^{2}}{2 \mathrm{~d}}(1-1 / \mathrm{k})$ C $Q=\frac{\varepsilon_{0} A V}{d}$ D $\quad E=\frac{V}{k d}$ As...

read more

A parallel plate capacitor with a dielectric slab of dielectric constant 3, filling the space between the plates, is charged to a potential V. The battery is then disconnected and the dielectric slab is withdrawn. It is then replaced by another dielectric slab of dielectric constant 2. If the energies stored in the capacitor before and after the dielectric slab is changed are \mathrm{E}_{1} and \mathrm{E}_{2}, then \mathrm{E}_{1} / \mathrm{E}_{2} is:
A \frac{4}{9}
B \frac{2}{3}
c \frac{3}{2}
D \frac{9}{5}

Correct option is B $\frac{2}{3}$ Let the charge stored by a capacitor with dielectric constant 3 be $Q$. Thus energy stored be $\frac{\mathrm{Q}^{2}}{2 \mathrm{C}_{1}}$ Since the charge remains the...

read more

The resistance required to be connected in parallel to an ammeter in order to increase its range 10 times, will be
A one-tenth the resistance of ammeter
B nine times the resistance of ammeter

C ten times the resistance of ammeter
D one-ninth the resistance of ammeter

Correct option is D one-ninth the resistance of ammeter Full scale deflection voltage be V Now initiall range is I $$ \mathrm{V}=\mathrm{IR} $$ Now, Range is made $10 \mathrm{I}$ $$ \begin{array}{l}...

read more

In the order of increasing frequency, the electromagnetic spectrum may be arranged as
A Gamma rays, \mathrm{X}-rays, visible light, radio waves
B \mathrm{X}-rays _{7} gamma rays, visible light, radio waves
C Radio waves, visible light, \mathrm{X}-rays, gamma rays
D Radio waves, visible light, gamma rays, \mathrm{X}-rays

Correct option is C Radio waves, visible light, $\mathrm{X}$-rays, gamma rays The electromagnetic spectrum is a continuum of all electromagnetic waves arranged according to frequency and wavelength....

read more

An electric dipole has the magnitude of its charge as q and its dipole moment is p. It is placed in uniform electric field E. If its dipole moment is along the direction of the field, the force on it and its potential energy are respectively
A q.E and max
B \quad 2 q . E and \min.
C q.E and \min
D zero and min.

Correct option is D zero and min. When the dipole is in the direction of field then net force is $\mathrm{q} \mathrm{E}+(-\mathrm{q} \mathrm{E})=0$ and its potential energy is minimum $=-$ p.E...

read more

1) The Bohr atomic model hypothesis made correct predictions for lower sized atoms like hydrogen, but poor spectrum predictions were achieved when larger atoms were taken into account. 2) When the spectral line is split into numerous components in the presence of a magnetic field, it fails to explain the Zeeman phenomenon.

1) The Bohr atomic model hypothesis made correct predictions for lower sized atoms like hydrogen, but poor spectrum predictions were achieved when larger atoms were taken into account. 2) When the...

read more

Consider the following statements :
(i) Soft iron conducts electricity
(ii) Soft iron is magnetic material
(iii) Soft iron is used for magnetic permanent magnets
(iv) Soft iron is used as electro magnet
A (i) and (ii) are correct
B (i) and (iii) are correct
C (ii) and (iv) are correct
D (i), (ii) and (iv) are correct

Correct option is D (i), (ii) and (iv) are correct Soft iron conducts electricity It is a magnetic material It is not used for magnetic permanent magnets It is used as electro magnet

read more

Two thin, long, parallel wires, separated by a distance ‘ \mathrm{d} ‘ carry a current of ‘ \mathrm{i}\mathrm{A} in the same direction. They will
A repel each other with a force of y_{0} \mathrm{i}^{2} /(2 \pi \mathrm{d})
B attract each other with a force of \mu_{n} \mathrm{i}^{2} /(2 \pi \mathrm{d})
C repel each other with a force of y_{0} i^{2} /\left(2 \pi \mathrm{rd}^{2}\right)
D attract each other with a force of \mu_{\mu_{1}} 1^{2} /\left(2 \pi \mathrm{d}^{2}\right)

Correct option is B attract each other with a force of $y_{0} i^{2} /(2 \pi \mathrm{d})$ $$ \frac{\mathrm{F}}{\mathrm{l}}=\frac{\mu_{0} \mathrm{i}_{1} \mathrm{i}_{2}}{2 \pi \mathrm{d}} $$ $$...

read more

Two very long straight parallel wires carry steady currents i and 2 \mathrm{i} in opposite directions. The distance between the wires is \mathrm{d}. at a certain instant of time, a point charge \mathrm{q} is at a point equidistant from the two wires in the plane of the wires. Its instantaneous velocity \vec{v} is perpendicular to this plane. The magnitude of the force, due to the magnetic field acting on the charge at this instant is:
A \frac{\mu_{n} i q v}{2 \pi d}
B \frac{\mu_{n} \text { iqv }}{\pi d}
C \frac{3 \mu_{n} \mathrm{iqv}}{2 \pi \mathrm{d}}
D zero

Correct option is (D) zero Magnetic field at P is perpendicu;ar to paper inward due to both the wires. Charged particle is also projected in the same direction. So, force on the charged particle is...

read more

Complete the following sentence : (I). A short-sighted person cannot see …………… object clearly. Short-sightedness can be correct by using ……….. lenses. (II). A long-sighted person cannot see ………….. object clearly. Long-sightedness can be corrected by using ………… lenses.

(a) A short-sighted person cannot see close objects clearly. Short-sightedness can be corrected by using the concave lens in front of the eyes. (b) A long-sighted person cannot see far objects...

read more