Internal Resistance
Q 1,2 & 3 Look up the answers in your text books.
Q4 Total R = 2 + 5.5
I = 1.5 V/Total R
Pd across cell = pd across external R = I(5.5) = 1.1V
Q5 emf = 1.5V
Lost volts = (1.5 – 1.2) V
Internal r = lost volts/0.30A = 1.0 ohm
External R = 1.2V/0.30A = 4.0 ohm
Q6 lost volts = 100A (0.04 ohm) = 4V
Only 8V across external circuit so bulbs are dim
Q7 I=V/R= 1.25V/25 ohm = 0.05A
Internal r = lost volts/I = 0.25V/0.05A = 5 ohms
Total R with 10 ohm = 10 + 5 =15
I = E/R = 1.5/15 = 0.1A
V across terminals= V across 10 ohm R = 0.1A(10 ohm) = 1V
