Energy, Power and Resistance Flashcards
What is potential difference?
Measure of transfer of energy by charge carriers
What is the equation used to find the voltage?
V=W/Q
How is a voltmeter connected in a circuit?
Parallel across a particular component
What would a perfect voltmeter have?
It would have infinite resitance so no current would pass through
Define potential difference in relation to EMF
Potential difference is used to describe when work is being done by the charge carriers, so when they lose energy as they go through an component
What does it mean if a component has a high p.d?
The higher the p.d the more energy per coulomb is transferred from electrical energy to other forms as the charges move through the component
What is electromotive force?
It is used to describe when work is being done on the charge carriers. Essentially the charge carriers are gaining energy as they pass through the component. The term is used when a charged particle gains energy from a source.
What is the equation for electromotive force?
E=W/Q
Describe how an electron gun works
A hot filament is heated by an electric current. The electrons in the filament then gain kinetic energy. Some of the electrons gain enough kinetic energy to escape the surface of the metal. If a p.d is applied between the filament and an anode, the filament acts as an anode. The emitted electrons then accelerate towards the anode, gaining kinetic energy. If there is a small hole in the anode, the electrons in line with this hole are able to pass through. This then creates a beam of electrons with a specific kinetic energy.
What is thermionic emission?
This is the emission of electrons through the action of heat.
What is Ohm’s Law?
For a metallic conductor kept at a constant temperature, the current in the wire is directly proportional to the p.d across its ends
How does increasing the temperature of a wire impact its resistance?
As you increase the temperature, the fixed ions begin to gain energy and vibrate. The frequency of collisions between the fixed ions and the moving electrons increases, and so the charge carriers do more work. In other words, they transfer more energy as they travel through the wire.
