Practice portal › Current Electricity › Cells, EMF and Internal Resistance
Asked in GSEB Board July 2017 · Terminal voltage and internal resistance
Given: I₁=0.9 A through R₁=2 Ω and I₂=0.3 A through R₂=7 Ω, from the same cell.
Idea: the emf ε and the internal resistance r are the same both times, so write ε=I(R+r) for each load and equate the two.
0.9 (2+r)=0.3 (7+r)
1.8+0.9 r=2.1+0.3 r
0.6 r=0.3, so r=0.5 Ω.
Check: ε=0.9×2.5=2.25 V and 0.3×7.5=2.25 V, the same emf from both readings.
Reading this solution needs no sign-in. You only sign in to practise against the clock and keep your progress.
Practise this with a timer