# Investigating Ohms law

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Introduction

Physics Coursework

Investigating Ohms law

## Introduction

Georg Ohm was born in Erlangden and educated at the university there. He became a professor of mathematics in 1817 in the polytechnic school of Nuremberg in 1833, and in 1852 became a professor of experimental physics in the university of Munich, where he later died.

In 1826, Georg Ohm discovered the current flowing through a metal wire was proportional to the potential difference across it (providing the temperature remained constant). Proportional means that if you double the potential difference the current will also double.

Ohms law:

Where:

‘V’ is the voltage in volts (V),

‘I’ is the current in amps (A),

‘R’ is the resistance in Ohms (Ω).

## Aim

In my coursework I will be looking at the following three components:

- A light bulb
- A thermistor
- A metal wire

My aim is to carry out experiments on these three components and find which component out of the three obeys Ohms law.

## Hypothesis

Ohms law gives the relationship between voltage, current and resistance in electrical circuits. Voltage is the push of the charges. Current is the flow of electricity. Resistance is the obstructions in the path of the current; therefore it slows the current down. There are four factors affecting resistance. They are:

- Length
- Cross-sectional area
- Material
- Temperature.

Middle

5

0.59

5

0.60

5

0.60

6

0.73

6

0.71

6

0.71

6

0.72

8

1.00

8

1.00

8

1.00

8

1.00

10

1.25

10

1.29

10

1.29

10

1.28

12

1.52

12

1.52

12

1.54

12

1.53

## Thermistor

Repeat 1 | Repeat 2 | ||||||

Voltage (V) | Current (mili amps) | Voltage (V) | Current (mili amps) | Voltage (V) | Current (mili amps) | Average voltage (V) | Average current (mili amps) |

0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |

2 | 6.00 | 2 | 5.10 | 2 | 6.60 | 2 | 5.90 |

3 | 8.60 | 3 | 7.30 | 3 | 8.90 | 3 | 8.27 |

4 | 11.30 | 4 | 9.70 | 4 | 11.70 | 4 | 10.90 |

5 | 14.20 | 5 | 12.10 | 5 | 14.50 | 5 | 13.60 |

6 | 17.20 | 6 | 14.90 | 6 | 17.70 | 6 | 16.63 |

8 | 23.80 | 8 | 20.80 | 8 | 24.20 | 8 | 22.93 |

10 | 39.00 | 10 | 34.10 | 10 | 39.60 | 10 | 37.57 |

12 | 67.50 | 12 | 65.80 | 12 | 69.80 | 12 | 67.70 |

### Light bulb

Repeat 1 | ## Repeat 2 | ||||||

Voltage (V) | Current (A) | Voltage (V) | Current (A) |

Conclusion

Evaluation

By doing this investigation, I have found many things. Firstly I found what voltage, current and resistance are and what effect voltage and current have on the resistance of different components. I have also found how resistance can be calculated and how three factors (voltage, current and resistance) can form a formula in relation to each other making either one the subject of the formula. I also learnt how to set up an ideal practical experiment, obtain my results, tabulate them, convert them to graphs, analyse them and interpret my graphs. I also learnt to implement safe working procedures using a variable resistor. This ensured that the component was not left on in the circuit for a long period of time.

There are also some improvements I could have made to my experiment in order for it to be even more accurate. One way I could have improved my experiment is by using a sensitive millimetre to obtain a very accurate set of results. I could have done is increasing my voltage in 1 volts in order to get more readings.

This student written piece of work is one of many that can be found in our AS and A Level Electrical & Thermal Physics section.

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