Starting Simple Circuits
FoundationBattery, wires and bulb must form a complete circuit for the light to shine; a switch opens and closes it to turn the lamp on and off.
- Current flows round a closed circuit, and the bulb lights.
- Closed makes a ring; open turns the lamp off.
- The switch controls opening and closing.
文體小知識：說明文帶你動手接駁簡單電路，認識通路和斷路，還有安全用電的規矩。
§Text Passage
1A battery stores electrical energy, and current flows along wires. To light a small bulb, the parts must form a complete ring called a closed circuit: current leaves the battery, passes through the wires and the bulb, and returns to the battery.
2A simple circuit needs three materials: one battery, two wires and one small bulb. Connect the battery's positive and negative terminals to the bulb's two contact points with the wires, and the bulb lights. If any joint comes loose, the current stops and the lamp goes out — an open circuit.
3Add a switch to the circuit: pressed, it closes the circuit and the lamp lights; opened, the circuit breaks and the lamp goes dark. The light switches at home and the buttons on the television work on the same principle.
4Observe the safety rules in circuit experiments: use low-voltage batteries only, never mains sockets; keep your hands dry; discard wires with broken covers; and put the batteries away afterwards. Remember: the power in wall sockets is strong, and primary students must never touch plugs or sockets.
1Summary 重點摘要
Battery, wires and bulb must form a complete circuit for the light to shine; a switch opens and closes it to turn the lamp on and off.
2Vocabulary cards Vocabulary
The part that stores electrical energy and powers a circuit.
The metal line that carries current, covered with insulation.
The glass bulb that glows when current passes through.
The electricity flowing along wires.
A complete circuit in which current can flow round the ring.
A circuit broken anywhere so the current stops.
The part that closes or opens a circuit.
The end of a battery marked with a plus sign.
The end of a battery marked with a minus sign.
3Step by step Steps
- Step 1: Prepare the materialsGet all the materials ready before the experiment: one one-point-five-volt battery, one small bulb, and two wires with their ends stripped; it also helps to lay a sheet of dry newspaper and arrange everything neatly. Some people think they can gather materials as they go, then find a wire missing halfway and panic. With the materials complete and tidy, wiring goes without mistakes, the experiment succeeds at the first try, and observation stays focused.
- Step 2: Build the closed circuitWhen wiring, tell the battery's positive and negative ends apart. Connect one wire from the positive terminal to the metal tip at the bottom of the bulb, and the other from the negative terminal to the metal screw on the side. All four joints must be firm, so the current can travel a full loop and form a closed circuit. Some think any loose twist will do, but a loose joint stops the current and the bulb stays dark.
- Step 3: Check the lightAfter joining the circuit, first see whether the bulb lights. A glowing bulb means the circuit works and current is flowing; if it stays dark, check every joint for looseness and whether the battery still has power. Some people assume a dark bulb must be broken, but more often a joint has simply come loose. Watching the light is the most direct way to judge a circuit, so form the habit of observing the result before hunting for the cause.
- Step 4: Make an open circuitAfter a closed circuit, make an open one to compare. Loosen any one wire and the loop of current is cut; the lamp goes out at once — that is an open circuit. Current must travel along an unbroken path and stops wherever the path breaks. Some think a battery and a bulb joined anywhere must light; this experiment shows that a break anywhere stops it all. It also explains why pulling down the main switch darkens every lamp in the house.
- Step 5: Add a switchA switch makes the circuit handier. Join it into the circuit: pressed, the contacts meet and the lamp lights; opened, the path breaks and the lamp goes dark, just like the light switch at home. Some people think controlling a lamp means unwiring it each time; with a switch we command the current at any moment without unwiring — convenient and safe. The switch is an important part of a circuit, and almost every appliance at home relies on one.
- Step 6: Tidy up safelyTidy up safely when the experiment ends. Take the wires off one by one, return the battery to its box, and put every material back in place. Never throw a battery into fire or put one in your mouth; hand used batteries to an adult or a recycling point. Some people think a finished experiment can be left anywhere, but safe tidying protects you and makes the next experiment worry-free and smooth.
4Diagrams Diagrams
5Worked example Example
Example: Long wired up his circuit, but the bulb will not light. How should he find the problem?
- First check whether the battery has power and whether the terminals have been reversed.
- Then check the four joints one by one for looseness or poor contact.
- Check whether the bulb is burnt out, and try a new one.
- Rule out the problems in order until the bulb lights up.
- Answer: Check in order — battery, joints, bulb — to locate the break and repair it, and the bulb will light. Changing only one thing at a time makes the fault easiest to find.
6Common mistakes Mistakes
7Quick check Quick check
Q1What is a working, lit circuit called?
Q2What is it called when the current stops and the lamp goes out?
Q3What materials does a simple circuit need?
Q4What does a switch do?
Q5May experiments use power from wall sockets?
8Recap Recap
- Current flows round a closed circuit, and the bulb lights.
- Closed makes a ring; open turns the lamp off.
- The switch controls opening and closing.
- Use low-voltage batteries and dry hands only.
- Mains power is dangerous — primary students never touch sockets.