A coil having $n$ turns and resistance $4R\,\Omega$ is connected with a resistance $R$. This combination is moved in time $t$ seconds from a magnetic field $W _ { 1 }$ weber to $W _ { 2 }$ weber. The induced current in the circuit is (1) $- \frac { W _ { 2 } - W _ { 1 } } { 5 R n t }$ (2) $- \frac { \left( \mathrm { W } _ { 2 } - \mathrm { W } _ { 1 } \right) } { 5 \mathrm { Rt } }$ (3) $- \frac { W _ { 2 } - W _ { 1 } } { R n t }$ (4) $- \frac { \mathrm { n } \left( \mathrm { W } _ { 2 } - \mathrm { W } _ { 1 } \right) } { \mathrm { Rt } }$
A coil having $n$ turns and resistance $4R\,\Omega$ is connected with a resistance $R$. This combination is moved in time $t$ seconds from a magnetic field $W _ { 1 }$ weber to $W _ { 2 }$ weber. The induced current in the circuit is\\
(1) $- \frac { W _ { 2 } - W _ { 1 } } { 5 R n t }$\\
(2) $- \frac { \left( \mathrm { W } _ { 2 } - \mathrm { W } _ { 1 } \right) } { 5 \mathrm { Rt } }$\\
(3) $- \frac { W _ { 2 } - W _ { 1 } } { R n t }$\\
(4) $- \frac { \mathrm { n } \left( \mathrm { W } _ { 2 } - \mathrm { W } _ { 1 } \right) } { \mathrm { Rt } }$