# Question Video: Using Ohm’s Law to Find the Current through a Resistor Physics • 9th Grade

The diagram shows a circuit consisting of a cell providing a potential difference of 20 V and a resistor with a resistance of 5 Ω. What is the current through the resistor?

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### Video Transcript

The diagram shows a circuit consisting of a cell providing a potential difference of 20 volts and a resistor with a resistance of five ohms. What is the current through the resistor?

In this question, we are given a diagram of an electric circuit, and we are asked to find the current through the resistor. We are given the potential difference that is provided by the cell, which is 20 volts, and the resistance of the resistor, which is five ohms. In order to solve this problem, we will need to use Ohm’s law. Ohm’s law states, for two points in a circuit, the potential difference across the points equals the current between the points multiplied by the resistance of the object between the points. Ohm’s law can be written as an equation, where 𝑉 stands for the potential difference across the resistor, 𝐼 stands for the current in the resistor, and 𝑅 stands for the resistance of the resistor.

To find the current, we must make the current 𝐼 the subject of the equation. We can do this by dividing both sides of the equation by the resistance. This gives us the equation current 𝐼 is equal to the potential difference 𝑉 divided by the resistance 𝑅. Before we begin putting in the given values, let’s take a look at the units in this equation. We have the unit of volts divided by the unit of ohms on the right-hand side and the unit of amperes, the unit of electric current, on the left-hand side. Since our units are correct, we can substitute our values for 𝑉 and 𝑅 to find the value of current. The current through the resistor is equal to 20 volts divided by five ohms, which gives us a value of four amperes. So our final answer is the current through the resistor is four amperes.