A closely wound search coil has an area of 3.12 cm2cm2 , 135 turns, and a resistance of 58.8 ΩΩ . It is connected to a charge-measuring instrument whose resistance is 43.4 ΩΩ . When the coil is rotated quickly from a position parallel to a uniform magnetic field to one perpendicular to the field, the instrument indicates a charge of 3.46×10−5 CC

B = 0.08395 T = 83.95 mT

Explanation:

According to the Faraday's law of electromagnetic induction, the induced emf is given as

E = -N (dΦ/dt)

The minus sign indicates that the emf is induced in a direction opposite to the changing magnetic flux.

Magnitude of emf is

E = N (dΦ/dt)

From Ohm's law

E = IR

But I = (dQ/dt)

E = R (dQ/dt)

N (dΦ/dt) = R (dQ/dt)

N dΦ = R dQ

Integrating both sides,

NΦ = RQ

But, Φ = BA

N BA = RQ

B = (RQ/NA)

R = 58.8 + 43.4 = 102.2 Ω

Q = (3.46×10⁻⁵) C

A = 3.12 cm² = (3.12 × 10⁻⁴) m²

N = 135

B = (102.2 × 3.46×10⁻⁵)/(135 × 3.12 × 10⁻⁴)

B = 0.0839534663 T = 0.08395 T = 83.95 mT

Hope this Helps!!!

when jerome paddle in flowing river towards east the net speed of jerome will increase

so the net speed of jerome will be given as

now the speed of paul will be same as it is given as he is running on the ground

so

so here we can say since the speed of jerome is more so he will win the race

now as we know the distance so the time difference is given as

so jerome will reach first and the time difference will be 203.55 s or 3.4 min