Moving charges
- Created by: theninjaemu
- Created on: 10-03-17 16:55
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- Moving Charges
- Electric current in metals
- Models describe the movement of charge carriers through materials
- In metals, electric current is the flow of electrons
- Most remain fixed to their atom
- Some are free to move (delocalised)
- Positive ions are fixed but are able to vibrate around points causing temperature rise
- The greater the rate of charge flow, the greater the electric current in the wire
- A larger current may be due to
- A greater number of electrons moving past a given point per second
- The same number of electrons moving faster
- Conventional current and electron flow
- Conventional current is the movement of current from a positive to a negative terminal
- Direction of all electric currents is still treated as positive to negative, regardless of movement of charge carriers
- In metals, electrons travel from the negative to the positive terminal, the opposite of conventional current
- Electric current in electrolytes
- Liquids that carry electric currents are called electrolytes. The charge carriers are ions
- Electrolytes are either molten ionic compounds or ionic solutions e.g. salt in water
- If a positive electrode (anode) and negative electrode (cathode) are placed in the solution, ions are attracted to them
- Positive ions (cations) move to the cathode
- Negative ions (anions) move to the anode
- There is a flow of charge, therefore, a circuit
- Cations accept electrons from the cathode and anions donate electrons to the anode. This means electrons can carry electric charge in the metal part of the circuit
- Measuring electric current
- Current at any point in a circuit is measured using an ammeter
- It is placed in series at the point the current is being measured
- They should have the lowest possible resistance
- Reduces the effect on the current it measures
- An ammeter with a high resistance reduces the current it is measuring
- 0 resistance means it has no effect on the current it measures
- Electric current in metals
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