Two coils having self-inductance of 30 H and 40 H are connected in series opposing connection. Find total inductance of the series connection, if the mutual inductance between the coils is 0.5 H.

This question was previously asked in
SSC JE Electrical 15 Nov 2022 Shift 2 Official Paper
View all SSC JE EE Papers >
  1. 63 H
  2. 69 H
  3. 35 H
  4. 30 H

Answer (Detailed Solution Below)

Option 2 : 69 H
Free
Electrical Machine for All AE/JE EE Exams Mock Test
7.7 K Users
20 Questions 20 Marks 20 Mins

Detailed Solution

Download Solution PDF

Concept

The equivalent inductance when connected in:

Case 1: Series addition

F1 Vinanti Engineering 11.01.23 D1

\(L_{eq}=L_1+L_2+2M\)

Case 2: Series opposition

F1 Vinanti Engineering 11.01.23 D2

\(L_{eq}=L_1+L_2-2M\)

where, L1 and L2 are self inductances

M is mutual inductance

Calculation

Given,  L1 = 30 H and L2 = 40 H

M = 0.5 H

\(L_{eq}=(30+40)-(2\times 0.5)\)

Leq = 69 H

Additional Information For a parallel circuit

The total inductance for parallel connection is given by:

\(L_{eq}={L_1L_2\space -\space M^2\over L_1\space + \space L_2 \space \mp \space 2M}\)

- sign is used for parallel addition

+ sign is used for parallel opposition

Latest SSC JE EE Updates

Last updated on Jul 1, 2025

-> SSC JE Electrical 2025 Notification is released on June 30 for the post of Junior Engineer Electrical, Civil & Mechanical.

-> There are a total 1340 No of vacancies have been announced. Categtory wise vacancy distribution will be announced later.

-> Applicants can fill out the SSC JE application form 2025 for Electrical Engineering from June 30 to July 21.

-> SSC JE EE 2025 paper 1 exam will be conducted from October 27 to 31. 

-> Candidates with a degree/diploma in engineering are eligible for this post.

-> The selection process includes Paper I and Paper II online exams, followed by document verification.

-> Prepare for the exam using SSC JE EE Previous Year Papers.

Get Free Access Now
Hot Links: teen patti vungo teen patti star login teen patti master plus