EMF of the source is 12 V, internal resistance 1 ohm, external resistance 5 ohm. Find the current in the circuit — Physics problems | PhysLabo
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Current in a complete circuit

Easy 10 grade Electricity / Complete Electrical Circuit
Problem statement

A source of emf $\varepsilon = 12$ V with internal resistance $r = 1$ ohm is connected to an external resistance $R = 5$ ohm. Find the current in the circuit.

Given
  • $\varepsilon = 12$ V
  • $r = 1$ ohm
  • $R = 5$ ohm
  • $I = ?$
Visual demonstration
Hints
Hint 1 / 2
Ohm's law for a complete circuit: $I = \varepsilon/(R + r)$.
Hint 2 / 2
The denominator contains the sum of the external and internal resistances.
Solution

Ohm's law for a complete circuit:

$$I = \frac{\varepsilon}{R + r} = \frac{12}{5 + 1} = \frac{12}{6} = 2 \text{ A}$$

Answer

$I = 2$ A

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