# To measure the resistance of a current, flowing through different lengths of Nichrome Wires

Extracts from this document...

Introduction

Science Coursework Andrew Robson

Resistance

Aim: To measure the resistance of a current, flowing through different lengths of Nichrome Wires

Prediction: I Predict that a shorter wire will have less resistance than a longer piece of the same substance.

Resistance is the property of any object or substance of resisting or opposing the flow of an electrical current. The quantity of resistance in an electric circuit determines the amount of current flowing in the circuit for any given voltage applied to the circuit. The unit of resistance is the ohm, the amount of resistance that limits the passage of current to one ampere when a voltage of one volt is applied to it. The standard abbreviation for electric resistance is R and the symbol for ohms in electric circuits is the Greek letter omega, .

The resistance of an object is determined by a property of the substance of which it is composed, known as the resistivity, and by the length and cross-sectional area of the object, and by the temperature.

Middle

OHM'S LAW

Current flows in an electric circuit in accordance with several definite laws. The basic law of current flow is Ohm's law, named after its discoverer, the German physicist George Ohm. Ohm's law states that, over a wide range of circumstances and materials, the amount of current flowing through a conductor is directly proportional to the electromotive force applied between the ends of the conductor. If resistance is defined as the ratio of electromotive force to current, then V = IR, where I is the current in amperes, V is the electromotive force in volts (see Electrical Units), then Ohm's law is equivalent to saying that R (which is measured in ohms) is a constant in the specified circumstances. A material for which this holds true is described as ohmic. Ohm's law can apply to electric circuits for both direct current (DC) and alternating current (AC), but additional principles must be invoked for the analysis of complex circuits and for AC circuits involving inductances and capacitances.

Conclusion

Variables:

The possible variables in this experiment are:

- The Amount Of Cells in the Circuit
- The Length Of The Wire
- The Settings Of The Variable Resistor

The independent variables for this experiment are the Number Of Cells and the length of the wire

The dependant variable is the amount of resistance in the circuit.

Safety Precautions:

Because we are dealing with electricity it is important to take safety precautions such as:

- Don’t Have Wet Hands When Constructing The Circuit.
- Make Sure Before We Start the experiment know how to use each piece of equipment safely to avoid shocks
- Don’t Play with the circuit layout and batteries to avoid shocks

### Apparatus: 3 cells, 1 variable resistor, connecting wires, crocodile clips,

### Nichrome wire, Ammeter, Voltmeter

Circuit Diagram:

### Method:

- We set up the circuit with 1 cell in
- We fixed the variable resistor so we could take a reading
- We tested 10mm of nichrome wire and took readings of the volts and amps
- We tested 20mm, 30mm and so on until we got to 1m of wire
- We set up the circuit with 2 cells in
- We took new readings on the wires
- We set up the circuit with 3 cells in
- We took new readings on the wires

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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