Faraday's law, induced emf and current
- A big circular coil of 1000 turns and average radius 10 m is rotating about its horizontal diameter at 2 rad s^-1. If the vertical component of earth's magnetic field at that place is 2 × 10^-5 T and electrical resistance of the coil is 12.56 Ω, then… Answer: 4. 1 A Maximum emf in a rotating coil is ε_max=NBAω , with the field component perpendicular to the axis (vertical component here).... 1
- A square loop of side 1 m and resistance 1 Ω is placed in a magnetic field of 0.5 T. If the plane of loop is perpendicular to the direction of magnetic field, the magnetic flux through the loop is : Answer: 3. 0.5 weber Flux is φ=BAcosθ . The plane of the loop is perpendicular to the field, so the normal is parallel to B and θ=0 . φ=0.5×... 1
- A 800 turn coil of effective area 0.05 m^2 is kept perpendicular to a magnetic field 5×10^-5 T. When the plane of the coil is rotated by 90^° around any of its coplanar axis in 0.1 s, the emf induced in the coil will be : Answer: 4. 0.02 V The coil starts perpendicular to the field (flux =NBA ) and, after rotating 90^° , lies parallel to it (flux zero). ε=Δφ/Δ... 1
- A uniform magnetic field is restricted within a region of radius r. The magnetic field changes with time at a rate d B/dt. Loop 1 of radius R>r encloses the region r and loop 2 of radius R is outside the region of magnetic field as shown in the figur… Answer: 3. -dvec B/dtπ r² in loop 1 and zero in loop 2 Induced emf is -dΦ/dt , and flux counts only the area where the field exists. Loop 1... 1