# Series & Parallel Circuits

12PHYS - Electricity

Finn LeSueur

2019

# Mahi Tuatahi

A circuit has current \(1.2A\) and voltage of 12V and has a single bulb.

- Draw the circuit and indicate current and conventional current directions.
- How many Coulombs of electrical charge flow through a point in every second?
- How much energy is used by the bulb in 5 seconds?
- What is the resistance of the bulb?

# Series Circuits

- The current has only one path to flow around
- The current is constant around the circuit
- The voltage is shared between the components in the loop

# Parallel Circuits

- The current has multiple paths to flow around
- The current is shared between paths
- The voltage is shared between components on each separate path

## Constructing Circuits

Use the PhET simulation to build these circuits:

- Create a series circuit with a bulb and a switch
- Create a parallel circuit with a bulb and a switch on each path, and one switch that controls the whole circuit.
- Measure the resistance of the circuit in PhET when you add resistors to the different circuit and try make a rule for what happens.

## Resistance in Circuits

- When you add resistors in series, the resistance
**increases**
- When you add resistors in parallel the total resistance
**decreases**

## Calculating Resistance

In series we can use this equation:

\[\begin{aligned}
& R_{T} = R_{1} + R_{2} + R_{3} + ...
\end{aligned}\]
In parallel we can use this equation:

\[\begin{aligned}
& \frac{1}{R_{t}} = \frac{1}{R_{1}} + \frac{1}{R_{2}} + \frac{1}{R_{3}} + ...
\end{aligned}\]
### Question 1

### Question 2

Calculate the values for each voltmeter, ammeter, as well as the total resistance of the circuit.