Electricity

Question 1

What happens to lattice ions as temperature increases

Answer 1

Lattice ions vibrate with a greater amplitude

Question 2

Why does resistance increases as temperature increases through a metal

Answer 2

The intensity (amplitude and speed) of vibrations increases. So, it is more difficult for free electrons to pass through as electrons are more likely to collide with lattice ions.

Question 3

What is an electron volt

Answer 3

Work done when an electron is accelerated through 1 volt

Question 4

Define EMF.

Answer 4

The energy supplied by a source per unit charge passing through the source, measured in volts.

Question 5

Define internal resistance

Answer 5

The unavoidable resistance any power source will have that makes it
harder for current to flow through the source. It causes energy to be dissipated in the source.

Question 6

Define current

Answer 6

The rate of flow of charge in a circuit, measured in Amperes

Question 7

What’s the max voltage of an A.C current?

Answer 7

325 V

Question 8

How to thermistors work.

Answer 8

As temperature increases the number of free charge carriers decrease. So the resistance of the thermistor increases and a larger fraction of voltage is across the thermistor

Question 9

What is Kirchhoffs first law

Answer 9

Sum of currents into circuit is equal to sum of current out

Question 10

Explain how current changes with time when a switch is closed in a circuit with a filament bulb and a cell.

Answer 10

• There is a fast increase in current
• Max current is reached as the bulbs resistance is lowest when switched on
  -Then current decreases as the resistance increases
• Resistance increases as temperature increases
• current levels off as thermal stability is reached