Q.

Consider I1 and I2 are the currents flowing simultaneously in two nearby coils 1 and 2, respectively. If L1 = self-inductance of coil 1, M12 = mutual inductance of coil 1 with respect to coil 2, then the value of induced emf in coil 1 will be          [2025]

1 ε1=L1dI1dt+M12dI2dt  
2 ε1=L1dI1dtM12dI1dt  
3 ε1=L1dI1dtM12dI2dt  
4 ε1=L1dI2dtM12dI1dt  

Ans.

(3)

ϕ1=L1I1+M12I2

ε1=dϕ1dt=L1dI1dtM12dI2dt

Magnitude of induced emf due to self-inductance, =LdI1dt

Magnitude of induced emf due to mutual inductance, =MdI2dt