Who was the first to observe the magnetic effect of electric current?

• Faraday

• Oersted

• Volta

• Ampere

At the centre of which of the following four circular rings the magnetic field is the strongest for equal magnitude of current?

• Loop 1

• Loop 2

• Loop 3

• Loop 4

The direction of the force on a current-carrying wire placed in a magnetic field depends on

• the direction of the current

• the direction of the field

• the direction of current as well as field

• neither the direction of current nor the direction of field

Magnetic field inside a long solenoid carrying current is

• same at all points (uniform)

• different at poles and at the centre

• zero

• different at all points

The magnetic field lines due to a straight wire carrying a current are

• straight

• circular

• parabolic

• elliptical

If current is passed in a spring with a weight hung on it, then the spring

• will be compressed

• will expand

• compression and expansion both will occur

• no change in the state of the spring

A straight wire of length 0.5m and carrying current 1.2A is placed in uniform magnetic field of induction 2T, applied perpendicular to the length of the wire. The force on the wire is

• 2.4 N

• 1.2 N

• 3.0 N

• 2.0 N

If a long copper rod carries a direct current, the magnetic field associated with the current will be

• only inside the rod

• only outside the rod

• both inside and outside the rod

• neither inside nor outside the rod

Two particles X and Y having equal charges, and accelerated through same potential and enters the uniform magnetic field describing circular paths of radii R₁ and R₂. The ratio of their masses of X and Y is :

• (R₁ / R₂) ^1/2

• R₂ / R₁

• (R₁ / R₂) ²

• (R₁ / R₂)

The cyclotron frequency of an electron gyrating in a magnetic field of 1 T is :

• 28 MHz

• 280 MHz

• 2.8 GHz

• 28 GHz