Table of Contents
What is the relationship between resistance and current?
The relationship between current, voltage and resistance is expressed by Ohm’s Law. This states that the current flowing in a circuit is directly proportional to the applied voltage and inversely proportional to the resistance of the circuit, provided the temperature remains constant.
Why current rating is important for rheostat?
The current rating is what limits how much power the rheostat will be able to dissipate, for any arbitrarily low resistance setting. Note that this is precisely what you would expect from a high-power load: the ability to cope with a high current draw.
Why is resistance inversely proportional to current?
If we regard the voltage (normalsize{V}) as fixed, then the resistance and current are inversely proportional, since their product is constant and equal to the fixed voltage. If we increase the resistance, then the current decreases, while if we decrease the resistance, then the current increases.
Why does current not decrease on passing through a resistance?
As far as I know current is the amount of charge passing per unit time. but the time component increases, i.e. it takes more time for the charge to travel through the resistor.
How does rheostat vary resistance?
As the slider moves, the effective length changes thereby changing the resistance of the rheostat. Since resistance is directly proportional to the length, as the effective length increases, the resistance increases. Similarly, as the effective length decreases, resistance offered by the rheostat decreases.
Does a rheostat change voltage or current?
Does a Rheostat change voltage? No, a rheostat doesn’t change the voltage of the circuit. One of the conditions for working of a Rheostat is to keep the voltage constant. As the Ohm’s law states- V= IR, where V is the voltage, I is current, R is resistance.
Why resistance is directly proportional to the current?
In other words, the current is directly proportional to the voltage and inversely proportional to the resistance. So, an increase in the voltage will increase the current as long as the resistance is held constant. If the current is held constant, an increase in voltage will result in an increase in resistance.
Why does current decrease when resistance increases?
The moving electrons can collide with the ions in the metal. This makes it more difficult for the current to flow, and causes resistance. When resistance is increased in a circuit , for example by adding more electrical components , the current decreases as a result.
Why does resistance reduce current?
The atoms in a resistor scatter and absorb the energy from the charge carriers in the current. So some of the average kinetic energy of the current is converted to heat in the resistor, and the current is reduced, compared to if the resistance wasn’t there.
As the current flows, the resistor absorbs part of the electrical energy and dissipates it as heat that increases the temperature of the resistor to a value higher than the ambient temperature. The power rating of a resistor indicates the maximum amount of energy it can dissipate without failing or degrading.
How is the temperature related to the power rating?
The curves provide data for the main operating and design conditions likely to be encountered. The power rating—as well as the derating curve—specifies the temperature up to which the maximum power rating is applicable (70°C).
How is the power rating related to the derating curve?
The power rating—as well as the derating curve—specifies the temperature up to which the maximum power rating is applicable (70°C). Also specified is the temperature at which the power rating must be derated to zero dissipation (150°C), which is also the maximum storage temperature of the resistor.
What should the stress ratio of a resistor be?
At temperatures above 70°C, the resistor is derated using the electrical stress ratio. Stress Ratio = Operating Power / Rated power. The recommended value is 80% for fixed resistors and 75% for variable resistors. The values at different temperatures are provided by the derating curves.