To determine the galvanometer’s internal resistor Rc and its

maximum electric current Ic , corresponding to a maximum

deviation of its needle, we mount it in series with a rheostat, as

shown in the adjacent figure.

When the needle makes a maximum deviation Vab = V1 = 5 V and

Rr = R1 = 80 kW. When the needle makes ½ maximum deviation

Vab = V2 = 2 V and Rr = R2 = 60 kW. When the needle makes ¼

maximum deviation Vab = V3 = 2 V and Rr = R3 .

a) (1 point) Write the relationship between V1 , R1 , Rc and Ic .

b) (1 point) Write the relationship between V2 , R2 , Rc and Ic .

c) (2 points) Write the relationship between V3 , R3 , Rc and Ic .

d) (2 points) Determine the values of Rc and Ic .

e) (3 points) Determine the value of R3