Olympiad Test: Electricity & Circuits - Class 6 MCQ

The third lamp Z is connected parallel to X, so the current gets divided among X and Z. So both bulbs X and Z light dimmer and the bulb Y lights brighter than earlier because current through it increases.

In an electric cell the metal cap is the positive terminal and the metal disc is the negative terminal. The direction of current will be P-Q-R-S because in an electric circuit the current flows from the positive terminal of the cell to the negative terminal.

In figure (A), both ends of the bulb are connected to the negative terminal of the cell. So, bulb will not glow while in figure (B) and (C), insulating objects like string and rubber band are used. So, the circuit is incomplete and bulb will not glow. Figure (D) represents the complete circuit with proper connection. Hence, the bulb glows in figure (D).

• P usually represents the glass bulb of the light bulb.
• Q likely refers to the filament or the metal wire inside the bulb.
• R is often the metal base or the part that connects to the electrical socket.
• S typically refers to the metal contacts at the bottom of the base.

In a light bulb, the insulator is generally the glass bulb because it helps contain the filament and electrical components safely, preventing electricity from flowing outside the designated parts.

Conductors are covered by the electric insulators to protect from electric shocks. They do not allow electric current pass through it. The plug cover R and connecting wires cover S are made of electrical insulators, whereas, P and Q are conductors.

Graphite is a conductor of electricity.

The wire that carries away the current from the power house (or electrical distribution system) and completes the circuit is called the neutral wire. It provides a return path for the current to the source after it has passed through the load (such as appliances or machines).

• Earth wire: This is used for safety to prevent electrical shocks by directing excess current to the ground.
• Live wire: This wire carries the current to the load from the power source.
• Neutral wire: This wire completes the circuit by carrying the current back to the power source after it has passed through the load.

A switch controls the flow of electricity in a circuit. It completes the circuit when "ON" (allowing current to flow) and breaks the circuit when "OFF" (stopping the current). Its main functions are to turn devices on or off and to ensure safety in electrical systems.

The air gap surrounding an electric circuit acts as an insulator. When electricity lights up a bulb, heat is produced. It works on the heating effect of current. The electrical conductivity of silver is maximum, it is the better conductor. We get an electrical shock because the human body is a conductor.

In X, the electrical energy is converted into sound energy. In Y, the electrical energy is converted into light energy. In Z, the electrical energy gets converted into heat energy. So, (C) is the correct option.

Insulators do not allow electric current pass through it. The rubber gloves are insulators of electricity. Hence, they prevent electric current to enter in our body and protect us from electric shocks. Human body is a conductor.

Cells are the sources of energy in the given diagram. Bulbs glow using the electrical energy from the cell. Replacing one cell with a piece of wire reduces the current in the circuit. Hence, the bulbs glow dimmer.

Fuse is a device used for short circuiting the circuit when overloading of current happens which helps to protect the electrical appliances.

A device by which an electric circuit can be easily completed or broken is called an electric switch or key. Electric current flows in the circuit when key is closed and stops when key is open. Hence, it is used to complete the circuit.

Brightness of bulb can be increased by increasing the current through the bulb. This can be achieved by connecting a similar battery in the circuit.

When the circuit is closed, an electric current starts flowing in the circuit from the positive terminal of battery. The current which passes through bulb P gets divided and flows in bulbs Q and R. As the brightness depends upon the current flowing through the bulb, so P will be bright but Q and R will be dim.

Since three bulbs X, Y and Z are connected in series and the switch is common for all bulbs, then all bulbs will glow simultaneously. Parallel circuit has multiple switches to operate individually.

From the diagram all the bulbs are connected in series. If Bulb Q is fused then circuit becomes open. Therefore, no current will pass through the circuit. Hence, none of the bulbs will glow in the circuit.

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.

- Aluminium: A metal that conducts electricity well due to free-moving electrons.
- Salt solution: Conducts electricity because dissolved ions allow electric current to pass.
- Ceramic articles: Typically insulators; they do not conduct electricity because they lack free-moving charges.
- Silver: An excellent conductor with high free electron availability.

Ceramic articles do not conduct electricity, making them suitable for insulating purposes in electrical applications.