From the above equation of resistance, it can be noted that the value of resistance increases with increase in the length of the conductor. A variable resistor rheostat can be used to control current in a circuit. A variable resistor consists of a length of resistance wire and an adjustable sliding contact. Without switching off the circuit, the resistance can be varied using a sliding contact. The symbol for a variable resistor is given in the diagram below.
A rheostat is made using a resistance wire, which is wound around circular insulation. A sliding contact is placed in the wire to change the length of the resistor. An end of the wire and sliding contact is connected to the circuit. As the length of the resistance wire is changed, the resistance also changes. The resistance can be set to any value from nearly zero to the total resistance of the wire in the variable resistor.
A rheostat is used in car lighting systems to change the brightness of the lights. The design of a potentiometer is similar to that of a variable resistor.
All the three points, both the ends of resistance wire and the adjustable contact, are connected to the circuit.
Two terminals and the contact are connected to the circuit. The length of the wire can be changed by the sliding contact. The resistance increases as the length of the wire increases. The resistance can be set to any value from zero to the total resistance of the wire. Potentiometers are often used, for example, to change the volume in a speaker system.
You can take measurements of current and potential difference, plot a graph of their IV characteristics, and find their resistance values. Download the file from the link below to see the Quick Guide to use the IV Characteristics of Devices experiment requires log in.
Download the file from the link below to see the full Instructions for the IV Characteristics of Devices experiment requires log in. The activity sheets can be downloaded using the link below requires log in. This contains details of the following:. Download the file from the link below to see the scientific Background to the IV Characteristics of Devices experiment requires log in. Understanding the electric resistance of metal wires is fundamental to being able to design electrical machines and electronic devices.
In this experiment, you can vary the effective length of a wire by moving an electrical contact and then go on to measure the wire's electric resistance by measuring potential difference and electric current on analogue dials. Electricity powers so much of our life today. It is vital to the design of power distribution networks over long distances to understand how the length of a metal wire affects its resistance.
On smaller scales, it is important to know how the length of a conducting wire changes its resistance for applications that use motors , from washing machines through to electric cars and industrial machines. Electricity is also used in heaters , from industrial furnaces for large-scale materials processing through to ovens, underfloor heating and kettles, and in all sorts of electronic devices , such as computers , screens and sensors. Designing any of these applications to be efficient and effective requires understanding how electricity flows through the materials in the various devices.
This FlashyScience gives an excellent introduction to this subject that is vital to our living today. Click below to download a pdf of the full instructions to use the Resistance experiment requires login. Physics Chemistry Electronics Materials Measurements. Ohm's Law. Press GO to launch the experiment! Resistors Resistors are the simplest and most commonly used electronic component and almost all electronic circuits them. Digital Multimeters Digital multimeters DMMs are versatile pieces of equipment commonly found in electronics, physics and engineering labs.
Application Quick Guide Full Instructions Questions Background Video Most electrical or electronic circuits use the voltage across the circuit components to perform some task. Or follow the brief instructions here: Click on the right hand wire post to move to the Select Wire screen.
Open the micrometer by dragging the thumbwheel down. Choose a material and drag the unlabelled wire into the micrometer. Close the micrometer and measure the wire's width. Click on the wire while it's in the micrometer to return to the main screen. Click on the switch to turn it on.
Measure voltage and current for a variety of contact positions on the wire. Calculate resistance for each contact position. Your rating is required to reflect your happiness. It's good to leave some feedback. Something went wrong, please try again later. Excellent questioning to ensure a good understanding of Potential Dividers.
Empty reply does not make any sense for the end user. Good scaffolding to help students understand the shared principles used in potential divider circuits.
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