When a resistor of resistance R is connected across a cell, the terminal p.d of the cell is reduced to three quarters of its e.m.f. The internal resistance of the cell is expressed as

JThomson

6 years ago

E=IR+Ir
IR=(3/4)E
Ir=(1/4)E
r=[(1/4)E]/I
4Ir=E
E=I(r+R)
4Ir=I(r+R)
4r=r+R
3r=R
r=R/3

joymaxwell

4 years ago

According to the question, V=3/4E
so E=4V/3 but E is also IR + Ir so E = V +Ir
4V/3 = V + Ir
4V = 3V + 3Ir
V = 3Ir
r =V/3I
r=IR/3I
r = R/3

IFEDEBO

10 years ago

is dat true

timothy09

12 years ago

i.e. 1/R+1/R+1/R=3/R =R/3. IS RESTITOR IM PARALLEL. THAKS