[highlight]
[b]Voltage[/b] - the difference in charge between two points.
[b]Current (Amps)[/b] - the rate at which charge is flowing. (It is the amount of [b]coulombs[/b] (6.24*10^18) passing a point in one second)
[b]Resistance[/b] - a material's tendency to resist the flow of charge (current).
[/highlight]
[highlight]
[b]Ammeter[/b]: an instrument for measuring electric current in amperes
[b]Voltmeter[/b]: an instrument for measuring electric potential in volts
[/highlight]
[h3]Ammeters[/h3]
[ul]
[li]Ideally have very low resistance, typically [approx] 0.01[ohm][/li]
[/ul]
[img src='https://res.cloudinary.com/deylrqt2d/image/upload/v1485722494/ammeters_1_wryzrw.svg']
[b]In a series circuit the current is constant[/b]
[img src='https://res.cloudinary.com/deylrqt2d/image/upload/v1485722741/ammeters_2_fdopxa.svg']
[b]In a parallel circuit the current splits of at the intersections of the wires, but overall the total current is still the same[/b]
[img src='https://res.cloudinary.com/deylrqt2d/image/upload/v1485724562/ammeters_3_k3jok5.svg']
The arrows just represent a point of measurement of the current.
[b]Also remember - "What goes into the junction leaves the junction"[/b]
[h3]Voltmeters[/h3]
[ul]
[li]Ideally have very high resistance, typically 10^5[ohm] to 10^6[ohm] (the higher the better)[/li]
[/ul]
When placed in series circuits, [b]voltmeters[/b] will prevent the circuit from functioning, as no current can get past the voltmeter, due to its high resistance.
[img src='https://res.cloudinary.com/deylrqt2d/image/upload/v1485726255/voltmeters_1_pnmyl2.svg']
[b]However in parallel circuits they work just fine[/b]
[img src='https://res.cloudinary.com/deylrqt2d/image/upload/v1485726255/voltmeters_2_v6omhv.svg']
[h3]Additional Notes[/h3]
[ol]
[li]The ammeter should be connected in a series circuit and should ideally have very low resistance to measure the current.[/li]
[li]A voltmeter should be connected in a parallel circuit and should ideally have a very high resistance to measure the potential difference.[/li]
[li]Current has to flow through a resistor to get to a bulb and once it has done so there is almost no current left for the bulb.[/li]
[li]The ammeter takes all of the current because of its very low resistance.[/li]
[/ol]
