R2: Factors affecting resistance- total amount of resistance

Question 1

Method (5p)

Answer 1

1) Set up circuit as shown
2) Close the switch momentarily and measure the current with an ammeter and p.d. with a voltmeter
3) Place results table and calculate the resistance
4) Now add a resistor in series as shown. Repeat step 2 and 3
5) Repeat step 2 but add resistor in parallel not series

Question 2

Effects of adding resistor in series (2p)

Answer 2

• Current decreases
• Resistance increases

Question 3

Why does resistance increase in series when adding a resistor

Answer 3

adding more resistors increases the total length of the electrical pathway,

Question 4

why does current decrease in series when adding a resistor

Answer 4

resistance acts as an obstacle to the flow of current

Question 5

Effects of adding resistor in parallel (2p)

Answer 5

• Current increases
• Resistance decreases

Question 6

Why does resistance decrease when resistor is added in parallel

Answer 6

adding more resistors in parallel provides more paths for current to flow

Question 7

Why does current increase when resistor is added in parallel

Answer 7

Ohm’s Law states that the lower the resistance, the higher the current.

Question 8

Ohms law for a resistor

Answer 8

current is directly proportional to the p.d. as long as the temperature of the resistor is constant

Question 9

Resistance in parallel circuits

Answer 9

The resistance is always less than the smallest resistor

Question 10

Resistance in series

Answer 10

The total resistance is the sum of resistance in the resistors
- Rt= R1 + R2