Spark: Static and Circuits

You need: 2 balloons on strings · a woollen jersey or cloth · tissue paper torn into small pieces · a tap with a thin stream of water · a ping-pong ball

1. Rub a balloon on the wool 20 times. Hold it just above the tissue pieces and watch.
2. Hold the charged balloon near (not touching) a thin stream of tap water.
3. Charge both balloons and hang them side by side. What do they do?
4. Roll a ping-pong ball across the table by moving the charged balloon in front of it.
5. Record what you saw at each station, then explain it using positive and negative charges.

How you'll know: You can explain each result: rubbing moved electrons onto the balloon, like charges pushed apart, and the charged balloon pulled on uncharged objects.

Safety: Balloons can burst: keep them away from faces. Some people have latex allergies: check first and use latex-free balloons if needed. Wipe up any water.

Go further: Test different rubbing materials (plastic bag, cotton, hair, wool) and rank which charges the balloon best.

You need: a clean glass jar · a card lid · a large paper clip straightened with a hook at the bottom · two thin strips of aluminium foil (1 cm × 4 cm) · a balloon or plastic comb

1. Push the straight end of the paper clip up through the card lid.
2. Hang the two foil strips side by side on the hook inside the jar.
3. Put the lid on the jar. Make a small ball of foil on the top end of the wire.
4. Bring a charged balloon near the foil ball. Watch the strips.
5. Touch the foil ball with your finger and watch again.

How you'll know: The strips spread apart when a charge is near, because they both get the same charge and repel each other. Touching the ball lets the charge escape and the strips drop.

Safety: Handle glass jars carefully. Bend wire with pliers to avoid pricking fingers.

Go further: Use the electroscope to compare which materials hold a charge longest.

You need: 2 AA batteries in a holder · a small torch bulb in a holder or an LED · 3 crocodile-clip leads · 12 test objects: coin, foil, key, plastic ruler, pencil lead, eraser, wooden peg, paper clip, glass, a leaf, cups of tap water and salty water

1. Build a circuit with a gap between two clips.
2. Predict whether each object will light the bulb.
3. Touch both clips to the object. Record whether the bulb lights, and how brightly.
4. Dip both clips into the tap water, then the salty water, without letting them touch.
5. Sort your results into conductors and insulators.

How you'll know: Metals and pencil lead (graphite) light the bulb; plastic, wood, rubber and glass do not. Salty water glows more than tap water.

Safety: Batteries only, never a wall socket. Keep water away from the battery holder and dry your hands afterwards.

Go further: Explain why electricians wear rubber-soled boots and why you should never touch a switch with wet hands.

You need: salt dough (flour, water, salt, cream of tartar) · sugar dough (flour, sugar, oil, distilled water) · 2 AA batteries in a holder with leads · LEDs

1. Make two lumps of salt dough. Push one battery lead into each lump.
2. Push the legs of an LED into the two lumps, long leg on the positive side.
3. Squash the lumps together. What happens to the LED? Why?
4. Separate them with a slice of sugar dough. Try again.
5. Design a dough creature with glowing eyes using both doughs.

How you'll know: The LED lights when the current has a path through the salt dough and goes out when the two lumps touch (a short circuit) or when the path is broken.

Safety: Doughs are for science, not eating. Check for wheat allergies. Wash hands afterwards.

Go further: Add two LEDs in parallel. Can you light both at once? Draw the circuit diagram.

You need: 2 AA batteries in a holder · 3 bulbs in holders · 8 crocodile-clip leads · a multimeter

1. Build a series circuit with one bulb. Rate its brightness from 1 to 5.
2. Add a second and third bulb in the same loop. Rate the brightness again.
3. Unscrew one bulb. What happens to the others?
4. Rebuild as a parallel circuit with each bulb on its own branch. Rate the brightness and unscrew one.
5. Measure the current and voltage in each version and record them.

How you'll know: In series the bulbs dim and all go out if one breaks. In parallel each bulb stays bright and the others keep working. Your meter readings back this up.

Safety: If a wire or battery gets warm, unclip it straight away: that means a short circuit.

Go further: Use your readings and V = I × R to show that adding bulbs in series increases the resistance.

You need: a cardboard tube or small plastic bottle · 2 AA batteries · a bulb or LED with holder · foil · a paper clip and two brass drawing pins (switch) · tape · a clear plastic lid

1. Draw your circuit diagram first: batteries, switch, bulb.
2. Make a switch from a paper clip that swings to touch a drawing pin.
3. Fit the batteries in the tube end to end and connect them to the bulb and switch.
4. Test it. Then time how long it stays bright, and test it after a light spray of water on the outside.
5. Improve one thing and test again.

How you'll know: The torch lights every time you flick the switch, you have a timed test result, and you can explain how the switch breaks and completes the circuit.

Safety: Never cut open or heat a battery. Remove batteries when not in use. Keep the spray test light and away from the open circuit.

Go further: Add a second LED in parallel for a wide beam and compare battery life.

You need: an audit checklist · a clipboard · a torch · the school's power bill or meter data (from the office) · a calculator

1. Pick two rooms. Count every light, heater, computer, screen and appliance.
2. Write down the watts shown on each label (ask an adult to help read labels on heavy items; never unplug anything yourself).
3. Note what is left on when no one is there and what glows on standby.
4. Estimate hours of use per day. Calculate energy: watts × hours ÷ 1000 = kilowatt-hours.
5. Rank the biggest users and write three recommendations.

How you'll know: You have a table of devices, a kilowatt-hour estimate for each and recommendations backed by your numbers.

Safety: Look, do not touch. Only the caretaker opens switchboards or meter boxes. Stay out of kitchens and workshops unless invited.

Go further: Use the power price on the bill to work out how much money one change could save in a year.