# Ohm's Law

## Resistance - N5 Recap

### In a previous section, the concept of electrical Current was covered. The flow of Charge around a circuit can be seen as similar to the flow of water through pipes. Using this analogy, Resistance can be thought of as the size of the pipe; the wider the pipe, the easier the water can flow through the system. The diagram below shows another analogy for Resistance of traffic being reduced from 3 lanes to 1 (the 'pinch point' represents the Resistor):- ## Measuring Current and Voltage

### In order to measure Current and Voltage within a circuit, the meters must be placed within the circuit in the correct positions:- ## Measuring Resistance of a fixed Resistor

### The experiment below shows a method for calculating the Resistance of a Resistor:- ### By varying the Power supply and measuring the Current and Voltage the following graph could be obtained:- ## Example 1 -

### A Circuit is set up as shown below:- ## Variable Resistors

### In the section above, the focus was upon Resistors of a fixed value., however, there are several other types of Resistor that will be used within this unit:- ### The above diagram shows the symbol for a variable Resistor. This type of Resistor can be set to a range of Resistances, generally by turning a dial on the component. This is therefore a manually controlled Resistor. ### The above diagram show the symbol for a Thermistor. This type of Resistor changes its Resistance due to the Temperature of the component. As the Temperature increases, the Resistance decreases. 