Callipers are used to measure the dimensions of objects with high precision and are often used in laboratories. Here you can learn how to use Vernier callipers to measure the widths of different samples.

Measurement is the starting point of meaningful scientific understanding. Callipers are common pieces of equipment used across science and engineering that allow object dimensions to be measured with a high degree of accuracy and precision. This can be vital for designing mechanical components or for experiments in which sample dimensions affect the outcomes, e.g. resistance or stress.

The following quick instructions are also in the downloadable file below:

- Drag moveable part of lower jaw to make jaw separation larger than sample width.
- Drag sample into lower jaws. Sample will snap into place.
- Drag moveable jaw blade to close jaws around sample.
- Read width from scale (see below for how to do this).
- Type width into ‘Sample Width’ text box and click ‘Check’ to see if you were right (green = correct, red = incorrect).
- Drag a sample out of the jaws (or press ‘Reset’) to return it to its original place and select a new sample.
- Click ‘New’ for a new set of samples with different widths.

To read the caliper scale (see full instructions for more details):

- Find the tick mark on the main scale (upper scale) that is just below the ‘zero’mark on the Vernier scale (lower scale). This gives a whole number of millimetres for sample width.
- Locate the tick mark on the Vernier scale that is most closely aligned with any tick mark on the main scale. This gives the number of tenths of a millimetre in the sample width.
- Add the values from the above steps to find the overall sample width.

Download the file below to view the full instructions for the Callipers experiment.

- Measure the width of ten samples. Check to see how many you measure correctly and give yourself a mark out of ten. Repeat this until you get 10/10 every time!
*Error analysis:*- Measure and record the width of ten or more samples.
- Use the width data to calculate the cross-sectional area of each sample.
- Determine the
*absolute error*and*fractional error*for each width measurement. - Determine the
*absolute error*and*fractional error*for each cross-sectional area value. *Statistical analysis:*- Measure and record the width of ten or more samples.
- Calculate the mean and standard deviation of the width measurements.
- (Advanced experiment) Calculate the
*standard error*of the width measurements and from this determine the confidence level of the mean.

Micrometers are used to measure the dimensions of objects with high precision. They are commonly used in laboratories. Here you can learn how to use micrometers to measure the widths of different samples.

Measurement is the starting point of meaningful scientific understanding. Micrometers are common pieces of equipment used across science and engineering that allow object dimensions to be measured with a high degree of accuracy and precision. This can be vital for designing mechanical components or for experiments in which sample dimensions affect the outcomes, e.g. resistance or stress.

The following quick instructions are also in the downloadable file below:

- Drag the
*ratchet screw*(right hand end) sideways to open or close the micrometer (the anvil part) in large steps (note that real

equipment doesn’t include this). - Click on the
*rotating**scale*and drag up or down to open or close the micrometer in small steps. - Open the micrometer and drag a sample into the anvil gap. The sample will snap into place.

- Close the micrometer around the sample. Make sure to follow use of the ratchet screw with the rotating scale to close the micrometer.
- Read width from scale (see below for how to do this).
- Type width into the appropriate text box and click ‘Check’ to see if you were right (green = correct, red = incorrect).
- Drag a sample out of the jaws (or press ‘Reset’) to return it to its original place and select a new sample.

You can also click ‘New’ for a fresh set of samples with different widths.

To read the micrometer scale (see full instructions for more details):

- Find the largest valued tick mark on the main scale that is revealed from behind the rotating thumbscrew. This gives a whole number of millimetres for sample width.
- Locate the tick mark on the rotating scale that is most closely aligned with the main scale axis. This gives the number of tenths of a millimetre in the sample width.
- Add the values from the above steps to find the overall sample width.

Download the file below to view the full instructions for the Micrometer experiment.

- Measure the diameter of ten ball bearing samples. Check to see how many you measure correctly and give yourself a mark out of ten. Repeat this until you get 10/10 every time!
*Error analysis:*- Measure and record the diameter of ten or more ball bearing samples.
- Use the width data to calculate the volume of each sphere.
- Determine the
*absolute error*and*fractional error*for each diameter measurement. - Determine the
*absolute error*and*fractional error*for each volume value. *Statistical analysis:*- Measure and record the diameter of ten or more ball bearing samples.
- Calculate the mean and standard deviation of the diameter measurements.
- (Advanced experiment) Calculate the
*standard error*of the diameter measurements and from this determine the confidence level of the mean.

Ohm's law is a fundamental equation that shows how voltage, electrical current and electrical resistance are related in simple conductors such as resistors. This experiments allows you to explore Ohm's law and how the coloured bands on resistors codes their resistance. In doing this you will also learn how to use a power supply and 'digital multimeters'.

Press GO to launch the experiment!

*Ohm’s law*

Voltage, current and resistance are the most fundamental quantities for describing the flow of electricity. Ohm’s law shows how these three quantities are related and so is a powerful way of understanding the basic nature of electricity.

This is relevant to vast areas of technology today, including national electricity grids, power generation, design of all electronic devices and all electronic circuits, heating, electrical safety and understanding of natural phenomena such as lightning. This experiment will allow you to explore Ohm’s law by making measurements of voltage, current and resistance.

*Resistors*

Resistors are the simplest and most commonly used electronic component and almost all electronic circuits them. They can be used to change the properties of any circuit they are part of, such as current flow, how voltage is distributed across components, the speed of a circuit, the amount of

amplification from a circuit, the response of a sensor or the amount of electrical heating from a circuit.

The simplest resistors are made of a thin film or wound wire of carbon or metal. They usually have a series of coloured bands that represents both

their target resistance value and how much the actual value might vary from this (the ‘tolerance’). This experiment lets you practise selecting the

appropriate colour bands on a resistor to achieve a certain resistance value.

*Digital Multimeters*

Digital multimeters (DMMs) are versatile pieces of equipment commonly found in electronics, physics and engineering labs. In this experiment you’ll learn how to use a DMM to measure voltage, current and resistance. You’ll see this piece of equipment in many other FlashyScience experiments!

Download the attached file for the Quick Guide including a table of resistor colour bands (requires log in) or follow these instructions:

**To measure resistance:**

- On the right-hand Digital Multimeter (DMM) rotate the switch to resistance measurement
- Click and drag the clips on the wires attached to the right-hand DMM so that they snap to the wires either side of the resistor (make sure the power supply is turned off)
- Note the resistance value shown on the DMM screen

**To change the resistor:**

- Double click the resistor to move to the
*Resistor Selection*screen

- Click on the colour band you wish to change

- Click on the palette colour you wish to select (see colour table in the attached file)

- Double click on the resistor to return to the main screen

**To use voltage and current:**

- Turn on the power supply (right hand side of screen) and turn the dial to set the voltage

- To measure
**current through the resistor**– turn the**left-hand DMM**dial to DC current

- To measure the
**voltage across the resistor**– turn the**right-hand DMM**dial to DC voltage

- NOTE: in this experiment the power supply voltage is also shown directly on its display

Please download the attached file for full operating instructions of the Ohm’s Law experiment (requires log in)

See attached file for questions on the experiment (requires log in)

Download attached file to see background information for this experiment (requires log in)

A potential divider is a simple circuit that uses resistors to supply a variable 'potential difference' (i.e. voltage).This can be used for many applications, including control of temperature in a fridge or as audio volume controls. Understanding how the resistors in the circuit allow this is important for designing many electronic circuits. Here you can investigate how changes in the two resistors can lead to different voltages across them.

Press GO to launch the experiment!

Most electrical or electronic circuits use the voltage across the circuit components to perform some task. This includes motors, sensors, speakers, computer chips, LEDs and diode lasers, communications antennas (e.g. in mobile phones), heaters, turbines, and mains electricity delivery to houses and industry.

It is important to know how to control the voltages in these circuits to make the applications work! The simplest circuit to start to understand this is the *potential divider*, which is made up of two resistors in series. Other circuits may be made of more advanced components but often use the same principles of how voltage (i.e. ‘potential’) division. For example:

Two *transistors* in opposite high or low resistance states and connected in series are used to define whether a ‘logic gate’ is set to a digital (‘Boolean’) value of 1 or 0, and are a fundamental building block of how a digital computer processor works.

Sensors can be made from a fixed resistor and a component that has a resistance that depends on whatever is being sensed connected, e.g. a *thermistor* for sensing heat or a *light-dependent resistor* for sensing light. A voltage applied to the two components in series allows the voltage across the fixed resistor to be a measure of the resistance of the sensing element’s resistance. This approach can avoid some difficulties of just using the single element, such as high power consumption.

Electrical heaters (including room heaters, cookers and hair dryers) use a fixed resistance *heating element* (e.g. a coil of wire) and a variable resistance *transistor *in series. The resistance of the transistor then controls how much voltage is across the heating element and, therefore, how much electrical heating is produced!

This experiment allows you to gain a good understanding of the *potential **divider*. It also allows you to reinforce your understanding of *Ohm’s law*, how *resistor* coloured bands code for resistance, and how to use *digital multimeters* (DMMs), which you may have already met in the FlashyScience *Ohm’s **law* virtual experiment.

Download the attached file to see the full Quick Guide (requires log in) or follow the instructions below:

**To measure resistance:**

- On the right-hand Digital Multimeter (DMM) rotate the switch to resistance measurement

- Click and drag the clips on the wires attached to the right-hand DMM so that they snap to the wires either side of either or both resistors (make sure the power supply is turned off)

- Note the resistance value shown on the DMM screen

**To change a resistor:**

- Double click the resistor you wish to change to move to the
*Selection*screen

- Click on the colour band you wish to change

- Click on the palette colour you wish to select

- Double click on the resistor to return to the main screen

**To measure voltage and current:**

- Turn on the power supply (right hand side of screen) and turn the dial to set the voltage

- To measure
**current through the resistor**– turn the**left-hand DMM**dial to DC current

- To measure the
**voltage across the resistor**– turn the**right-hand DMM**dial to DC voltage

- NOTE: the output voltage of the power supply is also shown on its display

Download the attached file to see the full operating instructions for the Potential Divider experiment (requires log in)

Download the attached file to see lots of Potential Divider questions and experiments (requires log in)

Download the attached file to see the Background to the Potential Divider experiment (requires log in)