Two wires carrying currents I₁ and I₂ lie, one slightly above the other, in a horizontal plane as shown in figure. The region of vertically upward strongest magnetic field is

Two parallel conductors carrying current of 4.0 A and 10.0 A are placed 2.5 cm apart in vacuum. The force per unit length between them is -

If an ammeter is to be used in place of a voltmeter, then we must connect with the ammeter a -

The magnetic field at the centre of a current carrying circular loop of radius R is B₁. The magnetic field at a point on its axis at a distance R from the centre of the loop is B₂. Then the ratio (B₁ / B₂) is