Key relationship
Series: εeq=nε, req=nr. Parallel: εeq=ε, req=r/n.
Physics · Class 12
Series and parallel cells
Series cells raise EMF but also add internal resistance. Identical parallel cells retain one-cell EMF while reducing internal resistance. Compare small and large loads.
Open the interactive experiment →Series and parallel cells
தொடர் மின்கலங்கள் EMF-ஐ உயர்த்தும். ஒத்த பக்க மின்கலங்கள் உள்ள்மின்தடையைக் குறைக்கும்.
Key notes, relationships and model limits
Remember
Series cells raise EMF but also add internal resistance. Identical parallel cells retain one-cell EMF while reducing internal resistance. Compare small and large loads.
Common trap
The equal-cell series and parallel formulas assume identical cells. Unequal EMFs can drive currents between parallel cells.
Model limits
Identical ideal EMF sources with identical nonnegative internal resistance, connected with agreeing polarities.
What you will learn
Use the controls and plotted relation to explain series and parallel cells.
Try the experiment
Try both scenarios, change one control, and predict the result before checking the graph and readouts.
Think of it this way
Change one input while keeping the others fixed, as you would in a controlled experiment.
Worked example
Three 1.5 V cells give 4.5 V in series and 1.5 V in parallel; internal resistances are 3r and r/3.
Why this matters
The model connects series and parallel cells with an observable reading. Check the equation and assumptions before applying it.
Before you start
SI units · algebra · graph reading
Check your understanding
Three identical parallel cells give combined EMF?
- Three times the EMF of one cell.
- The EMF of one cell.
- One third of the EMF of one cell.
Read the explanation
The EMF of one cell.
Course connection: Class XII Chapter 3. Consult the roadmap for CBSE, NEET, JEE Main and Advanced scope.