Question 11 Mark
How can a galvanometer be converted into a voltmeter?
Answer
View full question & answer→When a high resistance is connected in parallel to the galvanometer, it gets converted into a voltmeter.
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Question 21 Mark
The ratio between flux binding and current I passing through a coil of N turns is called $\left(\frac{ N \phi}{2}\right)$
Answer
View full question & answer→Inductance
Question 31 Mark
Write expression in vector form for produced magnetic field due to small part of a current carrying conductor in Biot-Savart law.
Answer
View full question & answer→ $\begin{array}{l}\overrightarrow{8 B}=\frac{\mu_0 I}{4 \pi r} \frac{\overrightarrow{\delta l} \times \vec{r}}{r^3} \\
or \overrightarrow{8 B}=\frac{\mu_0 I}{4 \pi r} \frac{(\overrightarrow{\delta i} \times \vec{r})}{r^2}\end{array} $
or \overrightarrow{8 B}=\frac{\mu_0 I}{4 \pi r} \frac{(\overrightarrow{\delta i} \times \vec{r})}{r^2}\end{array} $
Question 41 Mark
Show that no work is done by magnetic Lorentz force on a moving charged particle in magnetic field.
Answer
View full question & answer→It is because the direction of Lorentz force $\overrightarrow{ F }$ on charged particle is perpendicular to its velocity $\vec{v}$.e. displacement.
$\overrightarrow{ F }=q(\vec{v} \times \overrightarrow{ B })$, therefore, work done by the force is $W =\overrightarrow{ F } \cdot \overrightarrow{ d }= F d \cos 90^{\circ}=0$ hence no work is done.
$\overrightarrow{ F }=q(\vec{v} \times \overrightarrow{ B })$, therefore, work done by the force is $W =\overrightarrow{ F } \cdot \overrightarrow{ d }= F d \cos 90^{\circ}=0$ hence no work is done.
Question 51 Mark
A ring is uniformly charged. The total charge on ring is q and its radius is r. If it rotates on its axis by n rounds per second then what is the magnitude of produced magnetic field at the center?
Answer
View full question & answer→$B =\frac{\mu_0 t}{2 r}=\frac{\mu_0 q}{2 r T}=\frac{\mu_0 \omega q}{4 \pi r}$
Question 61 Mark
If on converting galvanometer of resistance G into ammeter, 1% of main current passes through the galvanometer, then what is the resistance of the shunt?
Answer
View full question & answer→$\begin{aligned} \mathrm{S} & =\left(\frac{i_g}{\mathrm{I}-i_g}\right) \mathrm{G}=\left(\frac{\frac{1}{100} \mathrm{I}}{\mathrm{I}-\frac{1}{100} \mathrm{I}}\right) \mathrm{G} \\ & =\left(\frac{1}{99}\right) \mathrm{G}=\frac{\mathrm{G}}{99} \text { Ans. }\end{aligned}$
Question 71 Mark
Which forces are produced by a moving charge (electron)? If electron is at rest then what type of fields are produced by it?
Answer
View full question & answer→A moving electron produces both electric and magnetic force fields whereas electron at rest produces only electric field.
Question 81 Mark
Area of a plane loop is A . Current I is flowing through it and it is located in a uniform magnetic field $\overrightarrow{ B }$. Obtain an expression for torque $\vec{\tau}$ acting on it. If this loop is free to rotate then what will be its orientation in stable position?
Answer
View full question & answer→$\vec{\tau}=\vec{m} \times \vec{B}$
If the direction of magnetic dipole is in the direction of magnetic field $\overrightarrow{ B }$, then electric current loop will be in stable position.
If the direction of magnetic dipole is in the direction of magnetic field $\overrightarrow{ B }$, then electric current loop will be in stable position.
Question 91 Mark
Write the direction $\otimes$ and $\odot$ of magnetic field produced at point $P$ in the given figure
Answer
View full question & answer→(A) The electric current or electric field going inside the plane of paper is represented by a cross $\otimes$.
(B) Electric current passing outside the plane of paper is represented by a dot $\odot$.
(B) Electric current passing outside the plane of paper is represented by a dot $\odot$.
Question 101 Mark
A plane loop of rectangular shape is moved in such a uniform magnetic field which is perpendicular to the plane of the loop. What is the direction and magnitude of induced current in the loop?
Answer
View full question & answer→If a plane loop is rotated in any uniform magnetic field which is perpendicular to the plane of the loop, then no current flows in the loop and hence there will be no direction
of the current.
Question 111 Mark
Two parallel wires are located very close to each other. The upper wire is fixed and the lower is free. What should be direction of current of suitable magnitude in both wires to stop the free wire? Give reason also.
Answer
View full question & answer→The current should flow in the same direction due to force of attraction.
Question 121 Mark
There is force of repulsion between two parallel current carrying conductors. What idea we get about direction of flow of current?
Answer
View full question & answer→Current in both wires is in opposite direction
Question 131 Mark
Which field is produced around a conductor due to electric current?
Answer
View full question & answer→Magnetic field
Question 141 Mark
A particle having charge $q$ is moving with a velocity $\vec{v}$ in a magnetic field $\vec{B}$. What is the magnitude of force acting on it?
Answer
View full question & answer→$\overrightarrow{ F }=q(\vec{v} \times \overrightarrow{ B })$
Question 151 Mark
If length, number of turns and current flowing through a solenoid are made doubled, then how many times will magnetic field becomes?
Answer
View full question & answer→Magnetic field will become twice.
Question 161 Mark
Electric current is flowing in north direction in an electric line. What will be direction of magnetic field due to electric current above the line?
Answer
View full question & answer→Direction of magnetic field will be towards east.
Question 171 Mark
Why a core of soft iron is used in a moving coil galvanometer?
Answer
View full question & answer→Intensity of magnetic field increases due to soft iгоп.
Question 181 Mark
What is the magnitude of magnetic field outside a current carrying solenoid?
Answer
View full question & answer→It is approximately zero.
Question 191 Mark
Value of $B$ depends on the value of $r$ Value of B decreases when $r$ increases. If $r=\infty$, then what will be the value of magnetic field B?
Answer
View full question & answer→Value of B will be zero
Question 201 Mark
Current I flow through two parallel straight wires in the same direction/The wires are at a distance 2r from each other. What is the intensity of magnetic field atw the midpoint between the two wires?
Answer
View full question & answer→Total magnetic field B = 0 as magnetic fields produced by two wires are equal and mutually opposite.
Question 211 Mark
If an electric current flows through a long copper wire, then what is the magnetic field inside the tube?
Answer
View full question & answer→Magnetic field will be zero
Question 221 Mark
How does produced magnetic field at any point depends on current flowing through a long and straight conductor?
Answer
View full question & answer→Magnetic field $B \propto$ current flowing ( $i$ )
Question 231 Mark
What is the direction of magnetic field at a point due to a long and straight current carrying conductor?
Answer
View full question & answer→It will be perpendicular to the line joining the point and the conductor as per right hand palm rule.
Question 241 Mark
What do you understand by specific charge?
Answer
View full question & answer→If mass of a particle is $m$ and charge on it is $q$. then the ratio $\frac{q}{m}$ is known as specific charge of the particle.
Question 251 Mark
What is the direction of magnetic field lines produced around a long current carrying conductor?
Answer
View full question & answer→Around the conductor in the form of closed curves.
Question 261 Mark
How is the magnitude of magnetic field inside a solenoid?
Answer
View full question & answer→It is uniform
Question 271 Mark
The spring used in a moving coil galvanometer is of low torsion constant. Why?
Answer
View full question & answer→Current sensitivity and voltage sensitivity of a galvanometer are inversely proportional to torsion constant of the spring. Its value is kept low to increase the sensitivity
Question 281 Mark
Name two factors by which voltage sensitivity of a galvanometer can be increased.
Answer
View full question & answer→(i) By increasing the number of turns N in the coil.
(ii) By decreasing the value of torsion constant C of the spring.
Question 291 Mark
One alpha rays beam is incident along positive direction of + X-axis. It experiences a force along + Y-axis due to magnetic field. What is the direction of magnetic field?
Answer
View full question & answer→Since alpha are positively charged particles, so their direction will be direction of current. Hence by Fleming's left-hand rule, the direction of magnetic field will be along Z-axis.
Question 301 Mark
An electron is not deflected while passing through a uniform magnetic field. What is the direction of magnetic field?
Answer
View full question & answer→Direction of magnetic field is either in the direction of motion of electron or opposite to it. Hence, $\theta=0^{\circ}$ or $180^{\circ}$ and therefore, $F = eVB \sin \theta=0$. So it will not be deflected.
Question 311 Mark
There are 1000 turns in 1 meter length of the core of a solenoid and a current of 2A is flowing through it. What is the magnitude of magnetizing field H?
Answer
View full question & answer→Given : $N=1000$ , $L =1 m$ , $I =2 A$
Magnetic field $H =\frac{ NI }{ L }$
$H =\frac{1000 \times 2}{1}=2000 A / m$
$=2 \times 10^3 A / m$ Ans.
Magnetic field $H =\frac{ NI }{ L }$
$H =\frac{1000 \times 2}{1}=2000 A / m$
$=2 \times 10^3 A / m$ Ans.
Question 321 Mark
Why a galvanometer is not used as an ammeter in the same form?
Answer
View full question & answer→Because the resistance of its coil is not very less and it can measure current corresponding to maximum possible deflection in the coil.
Question 331 Mark
Define one ampere in international unit system.
Answer
View full question & answer→One ampere is that electric current which in air or vacuum when flows through two long straight parallel wires at a distance of one meter produces a force of $2 \times 10^{-7} N / m$ in the wires.
Question 341 Mark
A battery of constant voltage is connected to the diametrically opposite ends of a circular coil. What is magnetic field at the center of the coil?
Answer
View full question & answer→Zero
Question 351 Mark
A charged particle enters a uniform magnetic field and parallel to its direction. What is the path of the particle?
Answer
View full question & answer→Rectilinear $\left(\because F=q v B \sin \theta\right.$, when $\left.\theta=0^0, F=0\right)$
Question 361 Mark
What is the relation between produced magnetic field at the center of a circular current carrying coil and its radius?
Answer
View full question & answer→$B \propto \frac{1}{ R }, \because$ Magnetic field at the center, $B =\frac{\mu_0 Nl }{2 R }$
Question 371 Mark
What is the direction of a current carrying solenoid when suspended freely in earth's horizontal plane?
Answer
View full question & answer→North-south (Current carrying solenoid behaves like a magnet)
Question 381 Mark
Write dimensional formula and unit of magnetic permeability of vacuum.
Answer
View full question & answer→$\left[ MLT ^{-2} A^{-2}\right]$
Unit : Henry/metre or newton/ampere ${ }^2$
Question 391 Mark
Write formula for Lorentz force on a charged particle passing through electric and magnetic field.
Answer
View full question & answer→$\overrightarrow{ F }=q(\overrightarrow{ E }+\vec{v} \times \overrightarrow{ B })$
Question 401 Mark
What is the magnetic field at O in the figure?
Answer
View full question & answer→B=0. Due to circular part, magnetic field is produced in opposite direction, hence resultant magnetic field is zero.
Question 411 Mark
Why does a magnetic force exerts on a conducting wire kept in a magnetic field on passing current through it?
Answer
View full question & answer→Due to flow of current, the free electrons of conducting wire moves in a definite direction with drift velocity and due to this magnetic force is exerted.
$ \overrightarrow{F}=(\overrightarrow{L} \times \overrightarrow{B})
$
Question 421 Mark
What is resultant magnetic field at point O in the figure?
Answer
View full question & answer→It will be zero due to both straight parts. Therefore, resultant magnetic field due to semicircular part is $B =\frac{\mu_o i}{4 r}$
Question 431 Mark
What is the magnitude of $K$ in the equation $d B=\frac{ Kidl \sin \theta}{r^2}$ in C.G.S. system?
Answer
View full question & answer→K = 1
Question 441 Mark
What is the magnitude of magnetic field at the center of a long hollow current carrying tube of copper?
Answer
View full question & answer→Zero
Question 451 Mark
Which physical quantity has newton/ampere- meter as unit? Is it scalar quantity or vector quantity?
Answer
View full question & answer→Magnetic field (vector)