Internal Resistance of a cell

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