Benjamin Franklin began experimenting with electricity during the 18th century - Leaving Cert Physics - Question 11 - 2022

An ammeter is an instrument used to measure electric current. It can also be referred to as a galvanometer or multimeter.

To draw the circuit diagram:

1. Represent the battery with two parallel lines, one longer (positive) and one shorter (negative).
2. For the light bulb, use a circle with a cross inside.
3. The switch can be represented by a break in the line with a dot where the two ends come close.
4. Connect these components with straight lines representing wires.
5. Make sure to show the battery connected to the switch and light bulb in series.

Wires in a circuit are made of metal because metals are good conductors of electricity. They have free electrons that can move easily, allowing the electric charge to flow with minimal resistance.

The charge carrier in a metal is the electron.

Current (I) can be calculated using the formula:

$I = \frac{Q}{t}$

where:

• $Q$ is the charge in Coulombs (C)
• $t$ is the time in seconds (s)

Substituting the values:

$I = \frac{30 C}{6 s} = 5 A$

The potential difference (V) can be calculated using Ohm's Law:

$V = I \times R$

where:

• $I$ is the current (5 A from part vi)
• $R$ is the resistance (3 Ω)

Substituting the values:

$V = 5 A \times 3 \Omega = 15 V$

The total resistance ($R_T$) for two resistors in parallel can be found using the formula:

$\frac{1}{R_T} = \frac{1}{R_1} + \frac{1}{R_2}$

where $R_1 = 3 \Omega$ and $R_2 = 2 \Omega$.

Substituting the values:

Resistance ($R$) is directly proportional to the length of the wire. Thus, if a piece of wire of length 1.5 m has a resistance of 12 Ω, the resistance of a 3 m piece can be calculated as:

$R = 2 \times 12 \Omega = 24 \Omega$

The resistance of a wire is inversely proportional to its cross-sectional area. This means that as the cross-sectional area increases, the resistance decreases and vice versa.