Track quiz
Show on a big screenHere are the ten rules from the lessons. Then try the questions.
| Idea | The rule |
|---|---|
| The invisible shape around a wire | A current-carrying wire has a magnetic field around it. The field forms rings round the wire. Reverse the current and the rings turn the other way. A bigger current makes a stronger field. The field is weaker farther from the wire. |
| Drawing the shape | Field lines are closed curves. Outside a magnet they run from N to S. Closer lines mean a stronger field. Two field lines never cross. |
| A magnet you can switch | A coil of many turns is a solenoid. Its field is strong and even inside. Outside, it looks like a bar magnet's field. More turns or more current makes the field stronger. It is a magnet only while current flows. |
| The field pushes back | A magnetic field pushes on a wire that carries current. Reverse the current or the field and the push reverses. The push is biggest when the wire is square to the field. Fleming's left-hand rule gives the direction. |
| Your house has a circuit | A house has live, neutral and earth wires. The fuse goes on the live wire. Appliances are joined in parallel. In normal use the earth wire carries no current. It carries current when there is a fault. |
| Two kinds of current | Direct current keeps one direction. Alternating current reverses direction again and again. Frequency is the number of cycles in one second, in hertz. In India the supply is alternating current at 50 Hz. |
| Motors | A motor changes electrical energy into motion. A split-ring commutator reverses the current every half turn. That keeps the coil turning the same way. |
| The field of a loop | Inside the loop, the field lines point the same way. At the centre, the lines are nearly straight. Take a coil of n turns, all one size and close together. Each turn carries the same current. At the centre, the field is n times that of one turn. A bigger current makes a stronger field. |
| Induction and the generator | A generator changes motion into electrical energy. A magnet moving near a coil induces a current in it. |
| Colours and ratings of house wires | Your book gives red for live, black for neutral, green for earth. A flexible cord may use brown for live and blue for neutral. An earth wire is marked green and yellow in Indian standards. Your book says a house often has two circuits. One is 5 A, for bulbs and fans. One is 15 A, for geysers and air coolers. |
A compass sits near a wire that carries current. You move the compass farther away. What happens to the needle's turn?
The battery of that circuit is reversed. What does the needle do?
Field lines are close together at one spot. What does that show?
Why can two field lines never cross?
How can you make a solenoid's field stronger?
A field runs left to right. The current runs into the page. Which way is the wire pushed?
Which wire carries the fuse in a house?
A heater is rated 1000 W at 220 V. Which fuse suits it?
The Indian supply is AC at 50 Hz. How many times does the current reverse in one second?
A magnet is held still inside a coil joined to a meter. What does the needle show?
What does the split-ring commutator do in a motor?
A hand-cranked torch has a generator. What energy change happens when you turn the handle?
A loop is seen from the front. The current goes clockwise. Which way does the field point through the loop?
Your book gives which colour for the live wire?
Read Chapter 12 in your Class 10 book. The next track is Our Environment.
Reveal every answer to finish this lesson.