Current Flashcards
Define the Ampere.
1 Ampere is 6.25x10^18 electrons passing a point every second.
(i.e. 1 A = 1 C/s)
What does Joule’s law state?
That the rate of heat produced is proportional to the square of the current (when resistance is constant).
What is electric current?
The flow of electrons.
Give a property of direct current.
It flows in ONE direction only.
Produced by cells and batteries
How does current flow according to conventional current?
How does current flow in reality?
- Conventional: Current flows from positive to negative.
- Reality: Current flows from negative to positive.
Give the formula for charge (in terms of current and time).
Q = I x t
Where is an ammeter placed in a circuit when measuring current?
In series. This is because current is constant throughout a series circuit.
What are the effects of current?
- Magnetic effect
- Heating effect
- Chemical effect
What is the significance of the heating effect of current?
- Massive amounts of heat can be lost through energy transfer across long distances.
- Electrical equipment can overheat/melt.
- Current can be used for heating objects via heating elements.
How do you demonstrate the magnetic effect of current?
- Place a compass on a wire.
- Switch on the circuit, the compass needle deflects.
- Switch off, returns to normal.
How do you demonstrate the chemical effect of current?
- Connect an anode (copper) and a cathode (zinc) plate to a power supply and run a current through the circuit.
- The copper anode dissolves and the iron cathode is coated in the copper ions.
- This is called ‘electroplating’.
How do you demonstrate the heating effect of current?
- Connect an insulated calorimeter to a power supply.
- Let a current flow through the circuit and measure the temperature over a set time with a digital thermometer.
- The current value will be proportional to the kelvin temperature.