The cross section of a hallway

There is no way they can alter the results because settings will be the same for each experiment. In this experiment only a direct current will be used. Experiment Plan In this experiment I have to test the following factors for differentiation of resistance in a wire.  Length  Cross-section width  Series  Parallel Nichrome wire is being used in this experiment. However, it is well-known for its high resistance as it is mainly used as a heating element. With this previous information of this material it will help making an accurate hypothesis and it should also be clear when problems occur.

Wires of different lengths will have to be tested to prove that resistance is in proportion to length. This should merely involve testing different lengths of one type of wire. There is no range perimeter to how long the lengths could be but it is uncertain that they will surpass 1 meter. Wires with different diameters need to be tested to prove that the resistance of a wire is inversely proportional to its area.

Get quality help now

WriterBelle

Verified writer

Proficient in: Electricity

4.7 (657)

“ Really polite, and a great writer! Task done as described and better, responded to all my questions promptly too! ”

+84 relevant experts are online

Hire writer

The only widths of wire that can be accessed are 0. 90mm, 0. 45mm, 0. 56mm and 0. 32mm. The experiment will obviously require an electrical circuit as the resistance of a wire in tan electrical circuit is being calculated.

To calculate the resistance of the wire using Ohm's Law, both an ammeter and a voltmeter will be required: Resistance = Voltage/Current The wire will be attached in a circuit in series so that the current flows directly through it. Power will need to be supplied through a DC power pack that enables the power to be changed easily and accurately.

Charges The charge is the amount of electricity traveling through a circuit. The symbol for charge is Q The unit for charge is Coulombs A capacitor is a device that stores charge Charge (Q) = Current (I) x Time (t) Current This is the flow of electrons round the circuit. This is measured in amps (I).

Voltage This is the driving force that pushes the current round. This is measured in volts (V) Resistance This is anything in circuit that slows the flow of current down. This is measured in ohms (? ). Ohm's Law shows that: Voltage (V) = Current (I) x Resistance (R) , so if the voltage increases then less current will flow, if the resistance is constant. Potential Difference It is the voltage across the terminal of cells, where the current is taken from it. P. d. is measured in volts. Voltmeter It is connected in parallel with resistors in the wire in a circuit. Ammeter It is connected in series to measure current. Symbols Cell: Switch:

Voltmeter: Resistor: Ammeter: Rheostat: Resistors Resistors (made of the length of nichrome wire) can be used to reduce the current in a circuit. A Variable Resistor or Rheostat A variable resistor or rheostat is used to vary the current in a circuit. Ohm's Law At a constant temperature the potential difference or voltage across the conductor is directly proportional to the current flowing through it. Resistance (R) in ohms (? ) Current (I) in ampere (A) Voltage (V) in volts (V) Resistors in Series: Resistors in Parallel: Note:  When resistors are connected in series the total resistance increases whereas it decreases in parallel.

When two resistors are connected in parallel then the total resistance can be calculated by the formula R= R1 R2/ R1 + R2 The modal of charge: All materials have some resistance to a flow of charge. A p. d. across the material causes free charges inside to accelerate. As the charges move through the material, they collide with the atoms of the material which get in their way. They transfer some or all of their kinetic energy, and then accelerate again. It is this transfer of energy on collision that causes electric heating. The longer a wire, the greater the resistance.

This is because the charges have further to go through the material; there is more chance of collision with the atoms of the material. In fact the resistance is proportional to the length of the wire, or R ? I Also, the thicker a wire is, the smaller its resistance will be. this is because there is a bigger area for the charges to travel through, with less chance of collision. In fact the resistance is inversely proportional to the cross-section area of the wire, or R ? 1/A This relations are illustrated in the figure: Cross Sectional Area The cross-sectional area of a conductor (thickness) is similar to the cross section of a hallway.

If the hall is very wide, it will allow a high current through it, while a narrow hall would be difficult to get through due to it's restriction to a high rate of flow. The animation at the left demonstrates the comparison between a wire with a small cross sectional area (A) and a larger one (A). Notice that the electrons seem to be moving at the same speed in each one but there are many more electrons in the larger wire. This results in a larger current which leads us to say that the resistance is less in a wire with a larger cross sectional area.

Length of the Conductor The length of a conductor is similar to the length of a hallway. A shorter hallway would allow people to move through at a higher speed than a longer one. Temperature The temperature of a conductor has a less obvious effect on the resistance of the conductor. Higher temperature means more vibrations. Imagine a hallway full of people. Half of the people (the electrons) are trying to move in the same direction you are and the other half (the protons) are evenly spaced but stationary in the hallway. This would represent a cold wire.

Since the wire is cold the protons are not vibrating much so the electrons can run between them fairly rapidly. As the conductor (hallway) heats up, the protons start vibrating and moving slightly out of position. As their motion becomes more unpredictable they are more likely to get in the way and break up the flow of the electrons. As a result, the higher the temperature, the higher the resistance. Length of wire: If I increase the length of the wire (keeping the thickness and the material of the wire same) there will be more atoms of the wire colliding with the electrons.