Correct Answer: B. Closed and complete

Explanation: For electric current to flow, there must be a closed and complete path from the positive terminal of the cell, through wires and components, back to the negative terminal. If the path is open or broken, the circuit is incomplete and no current can flow.

Correct Answer: B. Electric circuit

Explanation: An electric circuit is defined as the unbroken, continuous path along which current flows. It includes cells, wires, switches and other components connected in a loop.

Correct Answer: B. Both terminals of the cell are connected to the bulb in a complete loop

Explanation: The bulb glows only when there is a closed circuit. This happens when one terminal of the cell is connected to one end of the bulb and the other terminal to the other end with wires, forming a complete loop.

Correct Answer: C. Electric current flows in a closed circuit

Explanation: At Class 7 level, we simply learn that electric current flows only when the circuit is closed. In an open or broken circuit, there is no complete path, so current cannot flow.

Correct Answer: C. One of the wires is not connected properly to the bulb holder

Explanation: If any connection is loose or broken, the path of current becomes open or incomplete. In this case, the circuit is open even if the other parts are connected properly, so the bulb will not glow.

Correct Answer: B. Two terminals – positive and negative

Explanation: A simple electric cell (like a dry cell) has two terminals: a raised positive (+) terminal and a flat negative (–) terminal. Wires are connected to these terminals to complete a circuit.

Correct Answer: C. Positive terminal

Explanation: In circuit symbols, a cell is shown by a long line and a short line. The longer line represents the positive terminal (+), and the shorter line represents the negative terminal (–).

Correct Answer: D. As a cooking stove

Explanation: Electric cells are small sources of electricity used in devices like watches, remotes, torches etc. They cannot be used directly as a cooking stove, which needs a much larger amount of energy.

Correct Answer: B. It gets discharged and cannot provide current

Explanation: A cell has a limited amount of chemicals. After long use, the chemicals get used up, and the cell gets discharged. Then it can no longer provide sufficient current, and the torch stops working properly.

Correct Answer: B. Battery

Explanation: A battery is formed when two or more cells are connected together, usually in series. You often use batteries in toys, remote controls, and torches.

Correct Answer: B. Filament

Explanation: The part of a bulb that actually glows is the filament, a very thin wire inside the bulb. It becomes hot when current flows through it and starts glowing to give light.

Correct Answer: C. The metal base which acts as terminals

Explanation: The two thick wires attached to the filament are connected to the metal case and the metal tip at the base of the bulb. These act as the two terminals of the bulb through which current enters and leaves.

Correct Answer: B. Open

Explanation: A broken filament means there is a gap in the path of current inside the bulb. This makes the circuit open, so current cannot flow and the bulb does not glow.

Correct Answer: C. The bulb has two terminals: the metal tip and the metal case at the base

Explanation: An electric bulb has two terminals – the metal tip at the centre of the base and the metal case around it. They are connected to the filament through thick wires.

Correct Answer: B. Protect the filament and increase its life

Explanation: If normal air is present inside the bulb, the hot filament will quickly burn out. So the bulb is often filled with an inert gas or kept vacuum to protect the filament and make it last longer. (This is an extension of the Class 7 idea about construction of the bulb.)

Correct Answer: B. A small gap between the dots or line

Explanation: In circuit diagrams, a switch is shown as a small break in the line. When the switch is OFF, there is a gap, showing an open circuit. When ON, the gap is closed.

Correct Answer: B. A continuous line without gap

Explanation: A closed switch means the circuit is complete. In the diagram it is shown as a continuous line with no gap at the switch position.

Correct Answer: C. Cell → Wires → Bulb → Switch (forming a loop)

Explanation: A simple circuit should show a cell, bulb, switch and connecting wires arranged in a complete loop. The exact positions may vary, but they must form a closed path.

Correct Answer: C. When both terminals of the cell are connected to the bulb through a closed switch

Explanation: The bulb needs a complete path for current. When both terminals of the cell are properly connected and the switch is closed (ON), the circuit is complete and the bulb glows.

Correct Answer: C. Open or close the circuit as needed

Explanation: A switch does not supply energy but acts as a controller. It can make the circuit open (OFF) or closed (ON), thus controlling the flow of current.

Correct Answer: B. Conductors

Explanation: Substances which allow electric current to pass through them easily are called conductors. Most metals are good conductors.

Correct Answer: A. Copper metal

Explanation: Copper is a metal and a very good conductor of electricity. That is why copper wires are commonly used in electric circuits.

Correct Answer: B. Insulators

Explanation: Substances which do not allow electric current to pass through them are called insulators. Examples: rubber, plastic, glass, etc.

Correct Answer: B. Plastic or rubber

Explanation: Electric wires are made of metal (a conductor) but are covered with plastic or rubber (insulators) to protect us from electric shock and to avoid short circuits.

Correct Answer: C. Key (metal) – Conductor

Explanation: A key is usually made of metal, and metals are good conductors. Erasers and glass are insulators, and iron nail is a conductor (option A is wrong because it calls iron nail an insulator).

Correct Answer: B. Dissolved salts and impurities

Explanation: Pure water is a poor conductor, but tap water contains dissolved salts and impurities, which make it a better conductor of electricity.

Correct Answer: B. Connected in series in the same circuit

Explanation: When bulbs are connected in series, the same current flows through both. If one bulb’s filament breaks, the circuit becomes open and the other bulb also stops glowing.

Correct Answer: A. Circuit is complete and current is flowing

Explanation: A glowing bulb is a clear sign that the circuit is complete and electric current is flowing through the filament of the bulb.

Correct Answer: B. There is another path for current besides the switch

Explanation: If bulb glows even when the switch is OFF, it means the circuit is still complete through some other connection. This is sometimes called a short-circuit path bypassing the switch.

Correct Answer: B. The filament of the bulb is broken

Explanation: A broken filament means an open circuit inside the bulb. Even though outer connections may be correct, the current cannot flow through the filament, so the bulb will not glow.

Correct Answer: B. One after another such that positive terminal of one touches negative of the next

Explanation: Inside a torch, cells are connected in series. The positive terminal of one cell touches the negative terminal of the next, forming a battery that provides more energy than a single cell.

Correct Answer: B. Open or close the circuit inside the torch

Explanation: The torch switch makes or breaks the circuit between the cells and the bulb. When turned ON, the circuit is complete and the bulb glows; when OFF, the circuit is open and the bulb does not glow.

Correct Answer: B. The filament of the bulb is fused

Explanation: If the cells are new and placed correctly but the bulb still does not glow, the most common reason is that the filament is fused (broken), causing an open circuit inside the bulb.

Correct Answer: C. A doorbell

Explanation: A doorbell has a circuit with a cell or mains supply, wires, switch (the bell push) and the bell mechanism. When the switch is pressed, the circuit is complete and the bell rings.

Correct Answer: C. Doing electric experiments only under teacher’s supervision

Explanation: Electricity can be dangerous. So experiments should be done carefully and under the guidance of a teacher. Wet hands, damaged wires and careless overloading are unsafe practices.

Correct Answer: B. Plastic is an insulator and protects from electric shocks

Explanation: The outer part of plug tops and switches is made of plastic, which is an insulator. This prevents us from directly touching the metal parts carrying current and protects us from electric shocks.

Correct Answer: B. A cell, bulb, wires and the test material in the circuit

Explanation: To test conductivity, we make a simple circuit with a cell, bulb and wires. The material is placed in the circuit. If the bulb glows, it is a conductor; if not, it is an insulator.

Correct Answer: B. An insulator

Explanation: Since the bulb does not glow, it means no current is passing through the ruler in the circuit. So the ruler does not conduct electricity and is an insulator.

Correct Answer: B. Water is a good conductor when impure and may cause electric shock

Explanation: Water with impurities conducts electricity. If we touch switches with wet hands, current may pass through our body and give an electric shock. So it is a dangerous practice.

Correct Answer: C. Heart and nervous system

Explanation: Electric current passing through the body can affect the heart and nervous system, which can be very dangerous and even life-threatening. That is why electrical safety is very important.

Correct Answer: B. Whether the bulb is fixed properly in the holder and connections are tight

Explanation: If the bulb is not fixed properly or the connections are loose, the circuit may remain open even when the switch is ON. So we must check the connections and bulb fixing first.

Correct Answer: B. Glass, rubber, plastic

Explanation: Glass, rubber and plastic do not allow electric current to pass easily, so they are insulators. The other options contain metals which are conductors.

Correct Answer: B. Two cells in series and one bulb

Explanation: When two cells are connected in series, they provide more energy than one cell. With the same type of bulb, the bulb connected to two cells in series will usually glow brighter than with only one cell.

Correct Answer: B. Many pairs of long and short lines

Explanation: In circuit diagrams, a battery is shown by several pairs of long and short lines placed together, each pair representing one cell.

Correct Answer: B. Straight lines

Explanation: In circuit symbols, straight lines are used to show connecting wires between components like cells, bulbs and switches.

Correct Answer: B. Both terminals of the bulb are not connected to different terminals of the cell

Explanation: For current to flow through the bulb, one terminal of the bulb must be connected to the positive terminal of the cell and the other to the negative. Connecting both wires to the same terminal does not complete the circuit.

Correct Answer: D. Paperweight

Explanation: Electric bell, torch and electric iron all use electric circuits for their working. A paperweight is just a solid object used to keep papers in place and does not involve electricity.

Correct Answer: B. A circuit in which the path is broken and current cannot flow

Explanation: An open circuit has a gap or break somewhere. Because the path is not complete, no current can flow through the circuit.

Correct Answer: C. A circuit in which the path is complete and current can flow

Explanation: A closed circuit is a complete loop without any gap. In such a circuit, current can flow from the cell, through the devices, and back to the cell.

Correct Answer: C. Both terminals of the bulb connected to both terminals of the cell through wires forming a closed loop

Explanation: For the bulb to glow, the circuit must be closed. This is possible only when each terminal of the bulb is connected to a different terminal of the cell using wires, forming a complete loop for current to flow.