Studying the effect of intensity of exercise on fatigue

Equipment

stopwatch

Method

1. Perform some dynamic warm-up exercises on your non-dominant hand ('hand') to reduce the risk of muscle strain
2. Stretch your hand into the air above your head so that your arm is fully extended
3. Clench and unclench your hand at a frequency of one clench every two seconds
4. Record the time it takes for your hand to become completely fatigued - this is the point where it is too painful to continue
5. Rest the hand for two minutes
6. Repeat steps 2-5 but each time increase the frequency of clenching from one clench every two seconds to five clenches every two seconds in intervals of one clench every two seconds
7. Rest the hand for five minutes but each minute perform some static warm-down stretches on the hand
8. Repeat the entire process, steps 1-7, another two times to enable an average to be calculated
9. Perform some static warm-down stretches on the hand

Safety

The subject may develop muscle strain, so it is important that the warm-up and warm-down procedure is followed.

There are no other significant risks.

LDR response to variations in light intensity

Equipment

LDR
Multimeter
Connecting leads
Crocodile clips
Desk lamp
Metre rule
Blu-Tak

Method

1. Connect the LDR to the multimeter using crocodile clips and connecting leads.
2. Set the multimeter to read ohms.
3. Set the LDR up so it is 10 cm from the lamp. Ensure the lamp and the ruler are fixed in place to reduce errors in measuring distance.
4. Switch on the lamp and use the multimeter to record the resistance of the LDR. Switch off the lamp, then back on and repeat the readings. Repeat once more. Take a mean average of the three readings.
5. Increase the distance from the lamp to the LDR by 5 cm and repeat step 3.
6. Repeat step 4 until the LDR is 40 cm from the lamp.

Safety

The bulb being used may get hot.
The bulb is made of glass which may break.

Measuring the resistance of a light bulb

Depending upon your available equipment, there are a number of methods available.

All of the methods, though, rely on measuring a number of different voltage and current values, and then using the relationship V = IR to calculate the resistance.

Method 1
<jpg here of digital power supply circuit>

1. Set up the circuit as shown.
2. Turn on the digital power supply.
3. Increase the power supply from 0V to 12V in steps of 1V, at each increment measuring both the voltage across the bulb (in volts) and the current flowing through the bulb (in amps).
4. Repeat step 3 two more times.
5. Calculate an average current and an average voltage for each increment.
6. Use V = IR to calculate the resistance for each increment.
7. Plot your results on a graph, with current as the independent variable (horizontal axis) and the resistance as the dependent variable (vertical axis).

Method 2

(Remember - these are non-standard circuit symbols.)

1. Set up the circuit as shown.
2. Turn on the variable power supply.
3. Increase the power supply through its range of outputs, at each increment measuring both the voltage across the bulb (in volts) and the current flowing through the bulb (in amps).
4. Repeat step 3 two more times.
5. Calculate an average current and an average voltage for each increment.
6. Use V = IR to calculate the resistance for each increment.
7. Plot your results on a graph, with current as the independent variable (horizontal axis) and the resistance as the dependent variable (vertical axis).

Method 3 - this method does not allow for the use of averaging as a mathematical method.
<jpg here of potential divider circuit>

1. Set up the circuit as shown.
2. Turn on the power supply.
3. Increase the resistance of the potentiometer/rheostat in gradual stages, at each stage measuring both the voltage across the bulb (in volts) and the current flowing through the bulb (in amps).
4. Use V = IR to calculate the resistance for row of your table.
5. Plot your results on a graph, with current as the independent variable (horizontal axis) and the resistance as the dependent variable (vertical axis).