4.2.4 Resistance

Objective

Recall and use the equation for electrical energy: $E = I V t$

Understanding Electrical Energy

Electrical energy (E) is the amount of energy transferred when an electric current (I) flows through a circuit for a certain time (t) and a specific voltage (V).

The relationship between electrical energy, current, voltage, and time is fundamental in electricity.

The Equation: E = I V t

This equation states that the electrical energy (E) consumed is equal to the product of the current (I), the voltage (V), the time (t), and the power (P) dissipated.

We are focusing on the direct relationship between electrical energy, current, voltage, and time.

Components of the Equation

• Electrical Energy (E): Measured in Joules (J).
• Current (I): Measured in Amperes (A). The rate of flow of electric charge.
• Voltage (V): Measured in Volts (V). The potential difference that drives the current.
• Time (t): Measured in seconds (s). The duration for which the current flows.

How to Use the Equation

To calculate electrical energy, you need to know the current, voltage, and time. Ensure all units are consistent (e.g., Amperes, Volts, and seconds).

Example:

A current of 2.5 A flows through a circuit for 10 seconds when the voltage is 12 V. Calculate the electrical energy consumed.

1. Identify the given values:
   • I = 2.5 A
   • t = 10 s
   • V = 12 V
2. Apply the equation: $$E = I \times V \times t$$
3. Substitute the values: $$E = 2.5 \text{ A} \times 12 \text{ V} \times 10 \text{ s}$$
4. Calculate the result: $$E = 300 \text{ J}$$

Therefore, the electrical energy consumed is 300 Joules.

Table Summary

Quantity	Symbol	Unit	Description
Electrical Energy	E	Joule (J)	The amount of energy transferred.
Current	I	Ampere (A)	The rate of flow of electric charge.
Voltage	V	Volt (V)	The potential difference driving the current.
Time	t	Second (s)	The duration of current flow.