• Join over 1.2 million students every month
• Accelerate your learning by 29%
• Unlimited access from just £6.99 per month

# Characteristics of Ohmic and Non-Ohmic Conductors.

Extracts from this document...

Introduction

Characteristics of Ohmic and Non-Ohmic Conductors.

INTRODUCTION

## Conduction

Conduction takes place in solid matter of certain materials where energy can be transferred from atom to atom. A conductor is a material that allows an energy transfer of this nature to take place. All metals are good conductors of electricity, which is why all circuits contain mostly metal wires and components. When energy is supplied to one part of a conducting wire, the electrons in the wire move from one atom to the next, producing an electrical charge.  Semi-conductors are elements such as Silicon and Germanium, which do not conduct at low temperatures, and whose conductivity increases with the temperature.

## Current, Voltage & Resistance

Current electricity is the flow of charged particles through a circuit. In all dry conductors, the charged particles are electrons, therefore the charge is negative. The electrons in a circuit always flow from the negative terminal of a cell to the positive terminal. the same current flows through any given point in a series circuit, but in a parallel circuit, the current divides in a manner that the current in each of the separate branches sums up to the current in the main circuit. The size of the current in a circuit is measured in Amperes, or  “amps” using an ammeter.

Middle

The relationship between current, voltage and resistance

The relationship between current, voltage and resistance is expressed in Ohm’s Law, named after the physicist who discovered it. In the year 1826, George Simon Ohm conducted some experiments regarding current in conductors. As a result of these experiments he arrived at the conclusion that the current flowing through a metal wire is proportional to the potential difference across it (providing the temperature remains constant).

Ohm’s law simply translates to the equation:

#### V = I x R

or

Voltage = Current x Resistance.

• ## OHM’S LAW

Ohm’s law applies to metal conductors as well as certain other materials, and is obeyed provided that, not only the temperature, but all physical conditions remain constant. For example, the resistance of certain conductors will vary if they are bent or placed near a strong magnetic field. Certain conducting materials disobey ohm’s law entirely. These are mainly semiconductors and gases.

Conductors which follow ohm’s law are called Ohmic conductors, while those that disobey ohm’s law are known as Non-ohmic conductors.

### Ohmic conductors

Ohmic conductors are most easily identified by a graph plotted for the change in voltage against the change in current. These “V-I graphs” for ohmic conductors are seen as a straight line passing through the origin. This indicates that the increase in voltage is proportional to the increase in current, and thus indicates that ohm’s law is obeyed.

Conclusion

## The energy band theory

The key difference between semiconductors and conductors is that a conductor’s conductivity decreases with an increase in temperature, whereas a semiconductor’s conductivity increases with an increase in temperature. At any temperature above absolute zero, there is a possibility that an electron in the lattice will be knocked loose from its position, leaving behind a deficiency called a “hole”. If a voltage is applied, then both, the electron and the hole can contribute to a small current flow. As the thermal energy of the electrons increases, they breach the “hole” present in the semiconductor into what is called a conduction band. Thus, unlike with metals, in semiconductors, the resistance decreases with an increase in temperature. The conductivity of a semiconductor can be modeled in terms of the energy band theory. The theory suggests that at ordinary temperatures there is a possibility that electrons can reach the conduction band and contribute to electrical conduction.

## Intrinsic and extrinsic semiconductors

The term intrinsic distinguishes between pure semiconductors, and extrinsic (doped) semiconductors.

The conductivity of semiconductors such as Silicon (Si) can be increased by adding small, controlled amounts of impurities that have roughly the same atomic size that the semimetal itself. This process of adding impurities to increase conductivity is known as doping.

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

## Found what you're looking for?

• Start learning 29% faster today
• 150,000+ documents available
• Just £6.99 a month

Not the one? Search for your essay title...
• Join over 1.2 million students every month
• Accelerate your learning by 29%
• Unlimited access from just £6.99 per month

# Related AS and A Level Electrical & Thermal Physics essays

1. ## Investigate how the temperature affects the resistance of a thermistor.

If I ignore my anomaly and assume that the graph continues as it is I would image that at one point it would even out and the resistance would stop decreasing. This would either be at the point of no resistance because after this the resistance would be going into

2. ## Investigating the effect of 'length' on the resistance of a wire

I discovered after drawing graph No2 that a few of the points were slightly off the line of best fit. This can be explained as follows: * By measuring the voltage of both of the batteries used, I found out that their total voltage was 2.90V, this could be due

1. ## Investigation into the resistance of a filament lamp.

These include no running whilst experiments are in progress, hair tied back, jewellery tucked away and carrying out all experiments on benches clear of school books and standing up with stools tucked under benches. Also, as the potential difference is increased the more the current flows through the circuit.

2. ## Characteristics of Ohmic and non-Ohmic Conductors.

As voltage increases, current increases too. This is because as the voltage increases, more electrons have the energy to flow through the conductor, causing the current to increase simultaneously, (provided the temperature of the conductor remains constant). Voltage (V) V I Current (I)

1. ## Is polymer electronics the future of TV screens

Devices and Applications Organic Light-Emitting Diodes (OLEDs) One of the most current uses for polymer electronics is in the production of super-thin TV screens, known as OLEDs. OLEDs mainly consist of at least four different layers, a top and a bottom electrode with a semi conductive and electroluminescent organic layer in between.

2. ## resistivity if a nichrome wire

Voltage (volts) error (%) Current(amps) error (%) Resistance (ohm ?) errors (%) 0.100 0.001 0.37 4.05 0.24 4.17 1.548.22 0.200 0.001 0.75 1.33 0.24 4.17 3.135.50 0.300 0.001 1.231.22 0.24 4.17 5.135.39 0.400 0.001 1.59 1.89 0.24 4.17 6.636.06 0.500 0.001 2.00 2.00 0.24 4.17 8.336.17 0.600 0.001 2.33 0.43 0.24 4.17 9.714.62 0.700 0.001 2.71 1.11

1. ## Practical Project (2863/02): The Characteristics of a Shunt Wound Motor

The angular velocity is calculated by 2?f. The power is calculated from IV. And the efficiency is [(angular velocity * applied torque)/power]*100 Here are the results for my first set of readings: F0/N I/A F1/N F2/N F3/N F4/N f/Hz Angular Velocity/ rad/s Applied Torque/Nm Power Input/W Efficiency of Motor/% 2 1.49 3.2 0.5 1.0 3.1 16.7 104.9

2. ## The varying of the resistance of nichrome wire depending on its length

touch the nichrome while a current is passing through in case of getting burnt. * Do not use frayed or bare wires. * If gloves are used, they should not be plastic as this material can burn, instead use mittens. • Over 160,000 pieces
of student written work
• Annotated by
experienced teachers
• Ideas and feedback to
improve your own work 