How is the strength of the magnetic field at a point near a wire related to the strength of the electric current flowing in the wire?

(c) same at all points

The deflection increases. The strength of magnetic field is directly proportional to the magnitude of current passing through the straight conductor.

(d) The field consists of concentric circles centred on the wire. On applying right-hand thumb rule, we find the direction of magnetic field. The field is in the form of concentric...

An ammeter used for measuring an electric current flowing in an electric circuit.

The magnetic field lines near a long straight wire carrying current are concentric circles centred on the wire. So choice (iv) is correct.

If the current in the wire is increased, the deflection increases. The strength of magnetic field is directly proportional to the magnitude of current passing through the straight conductor.

The divergence, that is, the falling degree of closeness of magnetic field lines indicates the fall in strength of magnetic field near and beyond the ends of the solenoid.

(a) More the radius weaker the field. (b) Field strength is directly proportional to the number of turns in the coil.

The magnetic field lines of force are the lines drawn in a magnetic field along which a hypothetical north magnetic pole would move if it is free to do so....

(i) Yes, Alpha particles being positively charged constitute a current in the direction of motion. (ii) No. The neutrons being electrically neutral constitute no current.