A voltmeter with resistance rv is connected across the terminals of a battery of emf e and internal resistance r. Find the potential difference vmeter measured by the voltmeter.

V = I(R+r)

Explanation:

According to ohms law, the current (I) passing through a metallic conductor at constant temperature is directly proportional to the potential difference (V) across its end.

Mathematically, V= IR where V is the potential difference

I is the current

R is resistance

Given emf (E) = IRt... (1)

where E is the emf

Rt is the total equivalent resistance

The external resistance Rv is connected in series with the internal resistance 'r' to give total equivalent resistance Rt = (R+r)

Substituting in equation 1

E = I(R+r)

The equivalent potential difference V = I(R+r)

what experimental evidence led scientists to change from the previous model to this one?

a few of the positive particles aimed at a gold foil seemed to bounce back.

the colors of light emitted from heated atoms had very specific energies.

experiments with water vapor showed that elements combine in specific proportions.

cathode rays were bent in the same way whenever a magnet was brought near them.