Answer:
V = E - Ir
Explanation:
According to ohms law which states that the current I passing through a metallic conductor at constant temperature is directly proportional to the potential difference V across its ends. Mathematically,
V = IR... (1)
or E = IRt ... (2)
where;
V is the potential difference across the resistance R
E is the source voltage known as the electromotive force
I is the current
Rt is the effective resistance.
If a voltmeter with resistance Rohms is connected across emf E and internal resistance r, the external resistance and internal resistance will be in series with each other and their equivalent resistance Rt = R+r... (3)
Substituting equation 3 into equation 2 will give;
E = I(R+r)
E = IR+Ir ... (4)
Note that from equation 1, the potential difference V = IR
Substituting V = IR into equation 4 will result into;
E = V+Ir
V = E-Ir
The fore the potential difference V measured by the voltmeter is;
V = (E-Ir) meters
Answer:
Explanation:
Given:
Battery emf = E
Resistance of the voltmeter = R
Internal resistance = r
E = I× (R + r)
E = IR + Ir
Using ohms law,
Potential difference, V = IR
E = V + Ir
Making V the subject of formula,
V = E - Ir
Potential difference, V = E - Ir
