Current, Potential Difference and Resistance (3)

Question 1

Which lamp will be brighter at any potential difference?

Answer 1

A is brigher because it has a higher current than lamp B at any p.d. Therefore, A has a higher power output than bulb B

Question 2

Lamp B has the higher potential resistance at any potential difference. Explain how the figure above shows this

Answer 2

Lower current than Lamp A for the same potential difference and lower gradient than Lamp A

Question 3

Both lamps behave like ohmic conductors through a range of values of potential difference.
Use the figure above to determine the range for these lamps.
Explain your answer

Answer 3

0-2 volts as for an ohmic conductor current is directly proportional to potential difference so resistance is constant

Question 4

Which one of the following is most likely to include a thermistor?

Answer 4

3rd box (an automatic circuit to switch a heating system on and off)

Question 5

Why is it important that ammeters have a very low resistance?

Answer 5

So the ammeter reduced current as little as possible

Question 6

Scientists in different countries use the same temperature scale to measure temperature.
Suggest one advantage of doing this

Answer 6

Easier to share results

Question 7

One of the changes the student makes is to replace the thermistor with an LDR.
Describe what other changes the student should make to the apparatus

Answer 7

Replace Bunsen burner and water with a lamp and replace thermometer with light sensor

Question 8

It would not be safe to connect the electric cooker hob to the mains electricity supply by plugging it into a power socket.
Why?

Answer 8

Maximum current exceeds maximum safe current for a 2.5 mm squared wire

Question 9

An 18 V battery could not be used as the input of a transformer.
Explain why

Answer 9

Needs alternating current. Battery is direct current.