Q. No.Let \(\overrightarrow{\mathrm{E}}\)and \(\overrightarrow{\mathrm{B}}\)denote electric and magnetic fields in a frame S and \(\overrightarrow{\mathrm{E}}\) and \(\overrightarrow{\mathrm{B}}\) in another frame S' moving with respect to S at a velocity \(\overrightarrow{\mathrm{v}}\) Two of the following are wrong. Identify them.
(a) By’ = By + \(\frac{\mathrm{vE}_{\mathrm{z}}}{\mathrm{c}^{2}}\)
(b) Ey’ = Ey – \(\frac{\mathrm{vB}_{\mathrm{z}}}{\mathrm{c}^{2}}\)
(c) B’y = By + vEz
(d) E’y = Ey + vBz
Choose the correct option
1. (a), (b)
2. (b), (c)
3. (c), (d)
4. (a), (d)
(b) Ey’ = Ey – \(\frac{\mathrm{vB}_{\mathrm{z}}}{\mathrm{c}^{2}}\)
(c) B’y = By + vEz
(d) E’y = Ey + vBz
A vertical wire carries a current in an upward direction. An electron beam sent horizontally towards the wire will be deflected:
1. towards right
2. towards left
3. upwards
4. downwards
A current-carrying straight wire is kept along the axis of a circular loop carrying a current. The straight wire
| 1. | will exert an inward force on the circular loop |
| 2. | will exert an outward force on the circular loop |
| 3. | will not exert any force on the circular loop |
| 4. | will exert a force on the circular loop parallel to itself |
A proton beam is going from north to south and an electron beam is going from south to north. Neglecting the earth's magnetic field, the electron beam will be deflected:
| 1. | towards the proton beam |
| 2. | away from the proton beam |
| 3. | upwards |
| 4. | downwards |
A circular loop is kept in that vertical plane which contains the north-south direction. It carries a current that is towards the north at the topmost point. Let A be a point on the axis of the circle to the east of it and B a point on this axis to the west of it. The magnetic field due to the loop:
| 1. | is towards the east at \(A,\) and towards the west at \(B.\) |
| 2. | is towards the west at \(A,\) and towards the east at \(B.\) |
| 3. | is towards the east at both \(A,\) and \(B.\) |
| 4. | is towards the west at both \(A,\) and \(B.\) |
Consider the situation shown in the figure. The straight wire is fixed but the loop can move under magnetic force. The loop will:
| 1. | remain stationary |
| 2. | move towards the wire |
| 3. | move away from the wire |
| 4. | rotate about the wire |
A charged particle is moved along a magnetic field line. The magnetic force on the particle is:
| 1. | along its velocity |
| 2. | opposite to its velocity |
| 3. | perpendicular to its velocity |
| 4. | zero |
A moving charge produces:
1. electric field only
2. magnetic field only
3. both of them
4. none of them
Two parallel wires carry currents of \(20 ~\text A\) and \(40 ~\text A\) in opposite directions. Another wire carrying a current antiparallel to \(20 ~\text A\) is placed midway between the two wires. The magnetic force on it will be:
1. towards \(20 ~\text A\)
2. towards \(40 ~\text A\)
3. zero
4. perpendicular to the plane of the currents
Two parallel, long wires carry currents \(i_1,\) and \(i_2\) with \(i_1 > i_2.\) When the currents are in the same direction, the magnetic field at a point midway between the wires is \(10~\mu \text T.\) If the direction of \(i_2\) is reversed, the field becomes \(30~\mu \text T.\) The ratio of their currents \( i_1/i_2\) is:
1. \(4\)
2. \(3\)
3. \(2\)
4. \(1\)
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