Olympiad Test: Electricity And Circuits - 1 - Class 6 MCQ

In a zinc-carbon dry cell there is a electro-chemical reaction between zinc and manganese dioxide. A carbon rod collects the current from the manganese dioxide electrode. Thus chemical energy is converted into electrical energy. Option B is correct.

Substances which allow electricity to pass through them easily are called conductors of electricity or electrical conductors.For example:Silver,Copper,Aluminium,etc.

When Pooja connects the second cell in a simple circuit, then the second cell provides additional energy to the circuit, and the bulb gets more power to glow. Subsequently the brightness of the bulb increases.
For example, a torch with a single-cell provides less light compared to a torch with double cells.

Never join the two terminals of the electric cell without connecting them through a switch and a device like a bulb. If you do so, the chemicals in the electric cell get used up very fast and the cell stops working.

The metal cap and metal disc on an electric cell are positive terminals and negative terminal respectively.

Electric cells are used in alarm clocks, wrist watches, transistor radios, cameras and many other devices.

The torch is not glowing because either its bulb is fused or cells are connected wrongly or metal spring of torch does not make proper contact with the cell.

A potato is cut into two halves and the copper wires of a tester are inserted into it.  After half an hour, it was noticed that there was a greenish blue spot on the potato around one wire whereas there was no such spot around the other wire. They found that it was always the wire connected to the positive terminal, which had a greenish blue spot around it. This concept could be used for identifying the positive terminal of a cell or a battery concealed in a box.
Hence, A potato can be used to find the polarity of a cell and the statement is true.

An electrical insulator is a material whose internal electric charges do not flow freely and therefore make it very hard to conduct an electric current under the influence of an electric field.

A closed-circuit has every part made up of conducting material. In order to make the circuit work, the current should pass through every part of the circuit which is possible only when the materials are good conductors of electricity.

A switch is a device that is used for making and breaking electric current in a circuit. It is used to turn on and turn off daily used equipment like television, washing machine, fan, light, etc.

The statement is true. In a closed electric circuit, the electric current passes from positive terminal of the electric cell to the negative terminal.

Sometimes an electric bulb does not glow even if it is connected to the cell. It can be due to the following reasons - 

• Bulb has fused.
• Electric cell has stop producing electricity as the chemicals in the electric cell got used up.

The wires are not properly connected.

As can be seen in the figure.
In an electric circuit, the direction of current outside the cell is taken to be from the positive to the negative terminal of the electric cell.

When the switch is turned ON the circuit completes and the bulb starts to glow. When the switch is turned OFF the bulb does not glow. So circuit has two states on which the bulb depends. So we cannot determine by just connecting the switch in the circuit.

In the circuit here, bulb P will glow when the circuit is complete.
The circuit should not be broken at any point.It should be continous at every point.
At A only one path is present so A has to be closed in every situation.
But from B and C even if one switch is closed the circuit will be complete.And in case both B and C are closed even then the circuit will be complete.
Thus answers are:

• A  closed, B  closed and C  open.    OR
• A closed ,B and C both closed.

Thus, both option (B) and (C) are correct.
Correct option - (D).

When the switch is moved to the on position, the circuit is closed. All the bulbs will glow together.

When the switch is in the 'off'. position, no bulb will glow as the circuit is incomplete and no current flows through the circuit.Also these bulbs are in series which means that if current through one lamp is zero , current through every lamp will be zero and no bulb will light up.
Correct option is (D). 

The correct answer is option (d) Steel spoon. Steel is a good conductor of electricity.

• Current always flows from higher potential to the lower potential in a wire or through the load. The Circuit is the path in which current moves. 
• Circuit is basically the pathway of the current.
• It is analogous to the fact that water flows from higher side to the lower side. Similarly here also,  current moves from higher potential to the lower potential. The push is provided by a battery, just like water is pushed through a water pump.