Current loop and bar magnet as magnetic dipole, field along axis and equator
- A 2 amp current is flowing through two different small circular copper coils having radii ratio 1:2. The ratio of their respective magnetic moments will be Answer: 1. 1:4 Key idea: the magnetic moment of a current loop is M=IA=Iπ r² . The current is the same (2 A), so M∝ r² : M₁/M₂=(r₁/r₂)²=(1/2... 1
- An iron bar of length L has magnetic moment M. It is bent at the middle of its length such that the two arms make an angle 60^° with each other. The magnetic moment of this new magnet is: Answer: 3. M/2 Key idea: Magnetic moment = pole strength × distance between the poles. Bending changes this distance, not the pole strength.... 1
- The net magnetic flux through any closed surface is : Answer: 2. Zero Magnetic monopoles do not exist, so field lines always form closed loops: every line entering a closed surface also leaves i... 1
- A uniform conducting wire of length 12a and resistance 'R' is wound up as a current carrying coil in the shape of,(i) an equilateral triangle of side 'a'.(ii) a square of side 'a'.The magnetic dipole moments of the coil in each case respectively are… Answer: 1. √(3) Ia² and 3 Ia² Key idea: magnetic moment M=NIA , where N is the number of turns the wire of length 12a gives. Triangle (side... 1
- At a point A on the earth's surface the angle of dip, δ = +25^°. At a point B on the earth's surface the angle of dip, δ = -25^°. We can interpret that : Answer: 3. A is located in the northern hemisphere and B is located in the southern hemisphere. The angle of dip is positive (the north pole... 1