Resistance (T2)

Question 1

Why do we get resistance?

Answer 1

As electrons flow through a conductor, they can collide with the atoms of the conductor, causing resistance.

Electrons collide with atoms more often in a long wire than a short one.

A thin wire has fewer electrons to carry the current than a thick wire.

Question 2

Resistance in a wire increases as..

Answer 2

• the length of wire increases

- the thickness of the wire decreases

Question 3

Whilst voltage is the energy carried by the flow of electrons, resistance is…..

Answer 3

How much the material that the electrons are passing through tries to stop the flow of electrons.

Question 4

Define Ohm’s Law..

Answer 4

The current flowing through a resistor at a constant temperature is directly proportional to the voltage across the resistor.

ie: double the voltage and the current also doubles

Question 5

How would we set up a circuit to investigate Ohm’s Law?

Answer 5

• gather a voltmeter, an ammeter, a battery, a variable resistor and a switch
• set them up in series EXCEPT the voltmeter, which is connected in parallel, using a piece of wire to split the series
• with the switch closed, the readings on the ammeter and voltmeter are noted
• the value of the variable resistors is then altered and new readings are taken
• repeat this process 6 times
• place the results in a graph of current (I) against voltage (V)
• the graph should be in a straight line, telling us that the current flowing through the piece of wire is directly proportional to the voltage applied across its ends

Question 6

What happens to the relationship between current and voltage when investigating Ohm’s Law, if the temperature increases?

Answer 6

When current causes the wire to heat up, the atoms in the wire vibrate more vigorously, creating higher resistance by impeding the flow of electrons. So what was a straight line graph with current and voltage proportional to one another, starts to curve downwards as voltage stays the same but the flow of current slows.

Question 7

Why does resistance in a wire increase as the length of a wire increases?

Answer 7

Because there are more atoms for the electrons to collide with.

Question 8

Why does resistance increase as the thickness of a wire decreases?

Answer 8

Because in a thin wire there are less electrons to carry the current.