What is the relationship between Heat and Resistance and why? - Embibe
According to joul's Law H=I²RT where H= Heat, I= Current, R=Resistance, T= Time. Heat is directly proportional to resistance, if we change the resistance then . Heat= Power×time. now power= V²/R Therefore H is inversely proportional to R. Now Power is also I²R Therefore H is directly propo. Describe the effect of temperature on the resistance of an insulator. The effect of heat on the atomic structure of a material is to make the atoms vibrate, and the .
That's the power going into the resistor.
Electrical resistance and conductance - Wikipedia
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. 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.
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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.
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. 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. How Temperature Changes Resistance Although the resistance of a conductor changes with the size of the conductor e.
- Joule heating
- Electrical resistance and conductance
- Electric Resistance
This may be expected to happen because, as temperature changes, the dimensions of the conductor will change as it expands or contracts. 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.Resistivity and Resistance Formula, Conductivity, Temperature Coefficient, Physics Problems
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.
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.