An electron moves in a circular orbit with a uniform speed v.It produces a magnetic field B at the centre of the circle. The radius of the circle is proportional to

\(\sqrt{\frac{B}{v}}\)
^B⁄_v
\(\sqrt{\frac{v}{B}}\)
^v⁄_B

Solution

\(r=\frac{mv}{qB}\Rightarrow r\alpha \frac{v}{B}\)

A long solenoid carrying a current produces a magnetic field B along its axis. If the current is double and the number of turns per cm is halved, the new value of the magnetic field is

Solution

A charged particle moves through a magnetic field in a direction perpendicular to it. Then the

velocity remains unchanged
speed of the particle remains unchanged
direction of the particle remains unchanged
acceleration remains unchanged

Solution

Magnetic force acts perpendicular to the velocity.Hence speed remains constant.

Direction: Each question contains STATEMENT-1 and STATEMENT-2. Choose the correct answer(ONLY ONE option is correct ) from the following.

(a)Statement -1 is false, Statement-2 is true

(b)Statement -1 is true, Statement-2 is true; Statement -2 is a correct explanation for Statement-1

(c)Statement -1 is true, Statement-2 is true; Statement-2 is not a correct explanation for Statement-1

(d)Statement -1 is true, Statement-2 is false

Statement 1 : The magnetic field at the centre of the circular coil in the following figure due to the currents I₁ and I₂ is zero.

Statement 2: I₁= I₂ implies that the fields due to the current I₁ and I₂ will be balanced.

View Ans & Explanation
(d)Statement -1 is true, Statement-2 is false

Direction: Each question contains STATEMENT-1 and STATEMENT-2. Choose the correct answer(ONLY ONE option is correct ) from the following.

(a)Statement -1 is false, Statement-2 is true

(b)Statement -1 is true, Statement-2 is true; Statement -2 is a correct explanation for Statement-1

(c)Statement -1 is true, Statement-2 is true; Statement-2 is not a correct explanation for Statement-1

(d)Statement -1 is true, Statement-2 is false

Statement 1 : A cyclotron cannot accelerate neutrons.

Statement 2 : Neutrons are neutral.

View Ans & Explanation
(b)Statement -1 is true, Statement-2 is true; Statement -2 is a correct explanation for Statement-1

Neutrons are neutral.

Direction: Each question contains STATEMENT-1 and STATEMENT-2. Choose the correct answer(ONLY ONE option is correct ) from the following.

(a)Statement -1 is false, Statement-2 is true

(b)Statement -1 is true, Statement-2 is true; Statement -2 is a correct explanation for Statement-1

(c)Statement -1 is true, Statement-2 is true; Statement-2 is not a correct explanation for Statement-1

(d)Statement -1 is true, Statement-2 is false

Statement 1: If a charged particle is released from rest in a region of uniform electric and magnetic fields parallel to each other, it will move in a straight line.

Statement 2 : The electric field exerts no force on the particle but the magnetic field does.

View Ans & Explanation
(c)Statement -1 is true, Statement-2 is true; Statement-2 is not a correct explanation for Statement-1

Due to electric field, the force is \(\overrightarrow{F}=q\overrightarrow{E}\)in the direction of \(\overrightarrow{E}\). Since \(\overrightarrow{E}\) is parallel to \(\overrightarrow{B}\), the particle velocity \(\overrightarrow{v}\)(acquired due to force \(\overrightarrow{F}\)) is parallel to \(\overrightarrow{B}\). Hence \(\overrightarrow{B}\) will not exert any force since \(\overrightarrow{v}\times \overrightarrow{B}=0\) and the motion of the particle is not affected by \(\overrightarrow{B}\).

Direction: Each question contains STATEMENT-1 and STATEMENT-2. Choose the correct answer(ONLY ONE option is correct ) from the following.

(a)Statement -1 is false, Statement-2 is true

(b)Statement -1 is true, Statement-2 is true; Statement -2 is a correct explanation for Statement-1

(c)Statement -1 is true, Statement-2 is true; Statement-2 is not a correct explanation for Statement-1

(d)Statement -1 is true, Statement-2 is false

Statement 1 : If the current in a solenoid is reversed indirection while keeping the same magnitude, the magnetic field energy stored in the solenoid decreases.

Statement 2 : Magnetic field energy density is proportional to square of current.

View Ans & Explanation
(a)Statement -1 is false, Statement-2 is true

Reversing the direction of the current reverses the direction of the magnetic field. However, it has no effect on the magnetic-field energy density, which is proportional to the square of the magnitude of the magnetic field.

When a charged particle moving with velocity \(\overrightarrow{v}\) is subjected to a magnetic field of induction \(\overrightarrow{v}\), the force on it is non-zero. This implies that

angle between \(\overrightarrow{v}\) and \(\overrightarrow{v}\) is necessarily 90°
angle between \(\overrightarrow{v}\) and \(\overrightarrow{v}\) can have any value other than 90°
angle between \(\overrightarrow{v}\) and \(\overrightarrow{v}\) can have any value other than zero and 180°
angle between \(\overrightarrow{v}\) and \(\overrightarrow{v}\) is either zero or 180°

Solution

A proton moving vertically downward enters a magnetic field pointing towards north. In which direction proton will deflect?

East
West
North
South

Solution

Proton will represent the direction of current, so the direction of current is vertically downward. By Fleming's left hand rule, force acting on the proton in east direction.

An infinitely long straight wire contains a uniformly continuous current of 10A. The radius of the wire is 4 × 10 ^-2 m. The magnetic field at 2 × 10^-2 m from the centre of the wire will be:

Zero
2.5 × 10^{– 5} T
5.0 × 10 ^{– 5} T
none of these.

Solution

UnAttempted

0

Attempted

0

Correct

0

Wrong

0

Complete