Finding Current in a Series Circuit

Finding Current in a Series Circuit

1. In a series circuit, the current flow through each of the resistor is equal to the current flows through the whole circuit.
2. Potential difference (V) across the whole circuit is equal to the e.m.f. (E) if the internal resistance is ignored.
3. Effective resistance for the whole circuit = R₁ + R₂
4. By Ohm’s Law $$I=\frac{V}{R_1+R_2}$$

Example 1

For the circuit in the diagram above,

1. find the reading of the ammeter.
2. find the current flows through the resistor.

Answer:
a.
Potential difference across the 2Ω resistor, V = 12V
Resistance, R =2Ω
$$\begin{array}{l}V=IR\\ (12)=I(2)\\ I=6\Omega \end{array}$$
b.
The current flows through the resistor
= the reading of the ammeter
= 6Ω

Example 2

For the circuit above,

1. find the reading of the ammeter.
2. find the current flows through each of the resistors.

Answer:
a.
Potential difference across the 2 resistors, V = 12V
The equivalent resistance of the 2 resistors, R =6Ω
$$\begin{array}{l}V=IR\\ (12)=I(6)\\ I=2\Omega \end{array}$$
b.
The current flows through the resistors
= the reading of the ammeter
= 2Ω