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Multiple choice properties of magnet magnetic field moving charges and magnetism magnetic effects of current and magnetism physics

In a given region a charge particle is moving under the effect of electric and magnetic field with uniform velocity $\vec{v}=(\hat{i}+\hat{j}-\hat{k})$ m/s and magnetic field is given as $\vec{B}=(2\hat{i}+\hat{j}-2k)T$. The electric field is given as?

  1. $({i}+{j}-{k})$ V/m

  2. $({i}-{j}+{k})$ V/m

  3. $({i}+k)$ V/m

  4. $(-{i}-{k})$ V/m
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

We know Force $F=qE$------(1)

and also $F=qV\times B$-----(2)
From 1 and 2 we get 
$V\times B=E$
$V\times B$=\begin{matrix} \hat { i }  & \hat { j }  & \hat { i }  \ 1 & 1 & -1 \ 2 & 1 & -2 \end{matrix}
$V\times B=(-2+1)\hat { i } -(-2+2)\hat { j } +(1-2)\hat { k } $
$V\times B==-\hat { i } -\hat { k } $

Multiple choice properties of magnet magnetic field moving charges and magnetism magnetic effects of current and magnetism physics

A long, straight, $non-$ conducting string, painted with a charge density of $40\mu\ c/m$, is pulled along its length at a speed of $300\ m/s$. The magnetic field at a normal distance of $5\ mm$ from the moving string is $4.8\times {10}^{-1}\ T$

  1. $4.8\times {10}^{-1}\ T$

  2. Zero

  3. $\infty$

  4. Cannot be found
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A moving charged string is equivalent to a current I = lambda * v. Here, lambda = 40 * 10^-6 C/m, v = 300 m/s, so I = 40 * 10^-6 * 300 = 12 * 10^-3 A. B = mu0 * I / (2 * pi * r) = (2 * 10^-7 * 12 * 10^-3) / (5 * 10^-3) = 4.8 * 10^-7 T. The value in the question is 4.8 * 10^-1 T, which is incorrect.

Multiple choice properties of magnet magnetic field moving charges and magnetism magnetic effects of current and magnetism physics

 Two concentric circular coils of $10$ turns each are situated in the same plane. Their radii are $20$ cm and $40$ cm and carry currents of $0.2$ A and $0.3$ A respectively in opposite directions. The net magnetic induction field at their common centre is 

  1. $\cfrac {35\mu _0}{4}$

  2. $\cfrac {5\mu _0}{4}$

  3. $\cfrac {7\mu _0}{8}$

  4. $\cfrac {\mu _0}{80}$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The magnetic field at the center of a circular coil is B = (mu_0 * N * I) / (2 * R). For two coils with opposite currents, the net field is the difference between the two fields: B_net = (mu_0 * 10 / 2) * |(0.2 / 0.2) - (0.3 / 0.4)| = 5 * mu_0 * |1 - 0.75| = 5 * mu_0 * 0.25 = 1.25 * mu_0 = 5 * mu_0 / 4.

Multiple choice properties of magnet magnetic field moving charges and magnetism magnetic effects of current and magnetism physics

A coil having resistance $40 \Omega$, number of turns 100 and radius 6 mm is connected to an ammeter of resistance $160 \Omega$. The coil is placed perpendicular to the magnetic field. When the coil is taken out of the field, a charge of $32 \mu C$ passes through it. The intensity of magnetic field will be

  1. 6.55 T

  2. 5.66 T

  3. 0.655 T

  4. 0.566 T
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The total resistance in the circuit is R_total = 40 + 160 = 200 ohms. The charge passed is q = delta_phi / R_total, where delta_phi = N * B * A. Given q = 32 * 10^-6 C, N = 100, A = pi * (0.006)^2, we solve for B: B = (q * R_total) / (N * A) = (32 * 10^-6 * 200) / (100 * pi * 36 * 10^-6) = 64 / (36 * pi) approx 0.566 T.

Multiple choice properties of magnet magnetic field moving charges and magnetism magnetic effects of current and magnetism physics

The magnetic lines of force like electrical lines of force

  1. Are closed

  2. Are not closed

  3. Are open

  4. Are not open
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Magnetic lines of force are always closed loops, unlike electric lines of force which start from positive charges and end on negative charges (or infinity). Therefore, magnetic lines are not open.

Multiple choice properties of magnet magnetic field moving charges and magnetism magnetic effects of current and magnetism physics

Assertion: Basic difference between electric lines and magnetic lines of force is that former are discontinuous and the latter are continuous
Reason: No electric lines of forces exit inside charged conductor but magnetic lines do exist inside magnet

  1. Both A and R are true and R is the correct explanation of A

  2. Both A and R are true and R is not correct explanation of A

  3. A is true, but R is false

  4. A is false, but R is true
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Electric field lines are discontinuous because they terminate on charges. Magnetic field lines are continuous because they form closed loops and have no magnetic monopoles. The reason correctly explains the behavior inside conductors and magnets.

Multiple choice properties of magnet magnetic field moving charges and magnetism magnetic effects of current and magnetism physics

If a charged particle goes unaccelerated in a region containing electric and magnetic fields:

  1. ${\vec E}$ must be parallel to ${\vec B}$

  2. ${\vec V}$ must be perpendicular to Electric field

  3. ${\vec V}$ must be parallel to ${\vec B}$

  4. $E$ must be equal to $vB$.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

velocity must be perpendicular to B and d)E must be equal to vB. Explanation: Lorenz force is computed as F = q (E + v × B)

So, if particle is accelerated we must have qE = qvB and v × B = −vB First is possible when d is true and second is possible when d is true

Multiple choice properties of magnet magnetic field moving charges and magnetism magnetic effects of current and magnetism physics

An AC rms voltage of 2$\mathrm { V }$ having a frequeney of 50$\mathrm { KH }$ is applied to a condenser of capacity of 10 $\mu F$ The maximum value of the magnetic field between the plates of the condenser if the radius of plate is 10$\mathrm { cm }$ is

  1. 0.4$\pi \mu T$

  2. 4$\pi \mu T$

  3. 4$\mu T$

  4. 40$\pi \mu T$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The displacement current I_d = epsilon_0 * d(Phi_E)/dt. For a capacitor, I_d = I_c = V / X_c = V / (1 / (omega * C)) = V * omega * C. The magnetic field B at radius r is given by B * 2 * pi * r = mu_0 * I_d * (r^2 / R^2). Substituting values: omega = 2 * pi * 50 * 10^3, C = 10 * 10^-6, V = 2. I_d = 2 * 2 * pi * 50 * 10^3 * 10 * 10^-5 = 2 * pi Amps. At r = R = 0.1m, B = (mu_0 * I_d) / (2 * pi * R) = (4 * pi * 10^-7 * 2 * pi) / (2 * pi * 0.1) = 4 * pi * 10^-6 T = 4 * pi microT.

Multiple choice properties of magnet magnetic field moving charges and magnetism magnetic effects of current and magnetism physics neutral points magnetic poles and magnetic compass

The magnetic fields of atoms in a material are grouped together and aligned to form _________.

  1. Strong magnetic fields

  2. An area of magnetic field

  3. A region called magnetic domain

  4. A bar magnet
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

A magnetic domain is a region within a magnetic material in which the magnetization is in a uniform direction. This means that the individual magnetic moments of the atoms are aligned with one another and they point in the same direction.

The magnetic fields of atoms in a material are grouped together and aligned to form  region called magnetic domain