Track quiz
Here are the nine rules, in the words each lab uses.
| Idea | The rule |
|---|---|
| A wire warms up | Electric current warms any ordinary wire it flows through. Give two wires the same current. The one that is harder to get through warms more. A thin wire warms more than a thick one. More current warms it more. |
| Heat put to work | Heaters, irons and kettles use the heating effect on purpose. Each has a heating element. In a fan or a charger, the warmth is not wanted. |
| A wire made to fail | A fuse is a thin wire that melts easily. Too much current makes every part warm. A fuse of the right size melts first. The loop opens, and the current stops. |
| A wire becomes a magnet | A wire with current in it has a magnetic field around it. A compass needle swings. Turn the cell round, and the needle swings the other way. |
| More turns, more pull | Three things make a coil stronger. More current, an iron core, and more turns at the same current. Cells joined in a row give more current. |
| A magnet you can switch off | With an iron core, it is a magnet only while current flows. Switch off, and the pins fall. It has two poles, like a bar magnet. |
| A bell that rings itself | The coil pulls the arm, and the arm hits the gong. The same move breaks the contact. The coil lets go. A spring pulls the arm back. |
| Two metals and a liquid | A simple cell has two different metals dipped in a liquid electrolyte. A chemical reaction where the metals meet the liquid makes current. When its chemicals are used up, the cell is dead. |
| Cells that run down | A dry cell cannot be charged. A rechargeable cell can be charged, then works again. After many rounds, it holds less. |
The same current flows through nichrome and copper wires of one size. Which warms more?
A wire is made thinner. The current stays the same. What happens to the warming?
Which one uses the heating effect on purpose?
A cell, a switch and a lamp are in one loop. The switch is closed. Which effects does the current show?
A fuse of the right size is in the loop. Too much current flows. What happens?
A compass needle swings one way when the current flows. You turn the cell round. What happens?
A coil with an iron nail lifts 2 clips with one cell. You add a second cell in a row. It now lifts…
The switch of an electromagnet is opened. What do the clips do?
In an electric bell, what breaks the circuit?
Which pair of metals can make a cell with salt water?
Which cell can be charged and used again many times?
Chapter 4 is called Electricity: Magnetic and Heating Effects. Read it in your NCERT book.
Next: Exploring Forces. A magnet pulling a pin is a force.