Relation between heat energy and resistance - Electrical Engineering Stack Exchange
The resistance of a given object depends specific electrical resistance) of the material, Semiconductors lie between these two extremes. Resistivity varies with temperature. In an ohmic conductor (one that follows Ohm's law), electric resistance varies Originally Answered: What is relation between resistance and temperature?. Best electrical conductors: silver, copper, gold, aluminum, calcium, beryllium, In the case of copper, the relationship between resistivity and temperature is.
The only thing a resistor can do with that power is turn it into heat. However, heat power is not immediately temperature.
Let's say you have a fixed voltage or current applied to a fixed resistor. When the circuit is first turned on, the power into the resistor will cause its temperature to rise at a steady rate.
However, as the temperature of the resistor increases, it starts losing heat power to the air around it.
Electric Resistance – The Physics Hypertextbook
As that happens, it heats up more slowly because the total power into the resistor electrical power in minus heat power lost to the air goes down. The hotter it gets, the slower it heats up more. After you wait long enough, the system will be close enough to equilibrium or steady state so that you can't notice it changing anymore.
- Electric Resistance
- Temperature Coefficient of Resistance
- Electrical resistance and conductance
At that point, the heat power going out of the resistor to the air matches the electrical power going in. The net power into the resistor is 0, so it stays at the same temperature.Effect of Temperature on Resistance
By the way, this slowing movement to a steady state comes up often in physics and other sciences, and is called a exponential decay. In theory, the system never gets to steady state because that would take infinite time. In practice, eventually it gets close enough so that you don't care, can't measure the difference, or other sources of noise dominate so that the value is bouncing up and down little bits, but a lot more than the remaining distance to steady state.
Materials used for practical insulators glass, plastic etc.
They remain good insulators over all temperatures they are likely to encounter in use. These changes in resistance cannot therefore be explained by a change in dimensions due to thermal expansion or contraction.
Relationship between Resistance and Temperature
In fact for a given size of conductor the change in resistance is due mainly to a change in the resistivity of the material, and is caused by the changing activity of the atoms that make up the material. Temperature and Atomic Structure The reasons for these changes in resistivity can be explained by considering the flow of current through the material.
The flow of current is actually the movement of electrons from one atom to another under the influence of an electric field. Electrons are very small negatively charged particles and will be repelled by a negative electric charge and attracted by a positive electric charge.
Therefore if an electric potential is applied across a conductor positive at one end, negative at the other electrons will "migrate" from atom to atom towards the positive terminal. Only some electrons are free to migrate however. Others within each atom are held so tightly to their particular atom that even an electric field will not dislodge them.
Temperature Coefficient of Resistance | Physics Of Conductors And Insulators | Electronics Textbook
The current flowing in the material is therefore due to the movement of "free electrons" and the number of free electrons within any material compared with those tightly bound to their atoms is what governs whether a material is a good conductor many free electrons or a good insulator hardly any free electrons.
The effect of heat on the atomic structure of a material is to make the atoms vibrate, and the higher the temperature the more violently the atoms vibrate.
In a conductor, which already has a large number of free electrons flowing through it, the vibration of the atoms causes many collisions between the free electrons and the captive electrons.