Potential Difference Flashcards
What is potential difference?
The pd or voltage between two points in an electric field is the work required to move a charge of 1C from one point to the other. Measured is volts (V).
How do you connect a voltmeter to a circuit?
In parallel
Explain zero potential.
The Earth is considered to be such a huge mass that if you divide any charge against it, it will essentially be zero. Any connection to ‘earth’ is taken as zero potential. Any charge at very large distances are said to be so far apart as to be at zero potential according to Coulomb’s law.
What does emf stand for?
Electromotive force
What is electromotive force?
The emf is the voltage generated by the battery for the entire circuit. It exists within a battery or a power source.
Name four sources of emf.
- Primary cell
- Dry cell
- Secondary cells
- Mains electricity
How does a primary cell work?
It converts chemical energy to electrical energy. It consists of two different metal plates (electrodes such as zinc and copper) in an ionic solution (electrolyte such as sulphuric acid). The zinc releases positive ions into the electrolyte solution and the copper releases negative electrons. These are attracted. By connecting the two electrodes above the solution, a movement of electrons begins and current electrons. The negative electrode (zinc) is the cathode and the positive (copper) is the anode. This type of cell cannot be recharged.
How does a dry cell work?
A dry cell consists of two electrodes (such as zinc and carbon) and a paste electrolyte (sucha as manganese dioxide). One electrode froms the positive cap (carbon) and the other forms the negative base (zinc). The carbon rod is exposed at the top as the positive terminal and the bottom plate is the negative zinc can. Dry cells can be joined in a ‘battery of cells’ forming a multiple of pds. This type of cell cannot be recharged.
How do secondary cells work?
Also known as accumulators. Car batteries are an example of secondary cells. The lead plates are the electrodes and the sulphuric acid is the electrolyte. By reversing the current through them, they can be recharged. An alternator in a car achieves this. The combination of lead and acid produces the voltage. Other examples of secondary cells are lithium-ion batteries used in phones and other small devices.
How does mains electricity work?
Mains electricity is an alternating cycle of electricity produced by an oscillating coil/magnet. It produces a negative -> 0 -> positive sine wave cycle at 50Hz. The mains voltage in Ireland is 230V.
How does voltage work in a series circuit?
A voltage drop is the amount of voltage allocated to each component as it moves through the circuit. The sum of voltage drops in series equal the total voltage supple. All of the voltage will be used up by all the components.
How does voltage work in a parallel circuit?
Each parallel path carries the smae voltage. In the case of bulbs, the bulbs will shine brighter than if they were in series, but the battery will run out faster.
