Table of Contents
Chapter 14- Electric Current and Its Effects- Question and Answer -(Solved worksheet)
Question- Why does a bulb not light up in an open circuit, even when it is connected to a power source?
Answer- In an open circuit, the path for electricity is broken, preventing the flow of electric current to the bulb. In an open circuit, the switch is in the OFF position, breaking the continuous path required for electric current to flow, much like a closed gate would stop traffic on a road.
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Question- What happens to the flow of electric current when the switch in a circuit is turned from ON to OFF?
Answer- The flow of electric current stops. Turning the switch OFF opens the circuit, breaking the path for electricity and stopping the current flow, similar to how turning off a valve stops the flow of water in a pipe.
Question- How is a broken filament in a bulb represented in a circuit diagram?
Answer- By a broken or incomplete connection in the circuit. In a circuit diagram, a broken filament, which interrupts the flow of electricity, is shown as a broken or incomplete connection, indicating that the bulb is fused or its filament is broken.
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Question- In a circuit diagram, what does it mean when a cell or battery is represented by parallel lines?
Answer- The lines indicate the positive and negative terminals of the cell or battery.
Parallel lines in a circuit diagram represent a cell or battery, with the different lines indicating the positive and negative terminals, essential for establishing the direction of current flow.
Question- What could be the reason for a bulb not lighting up even if the circuit is closed and the bulb is functional?
Answer- There might be a problem elsewhere in the circuit, like a broken wire or a dead battery. If the bulb is functional and the circuit is closed but the bulb does not light up, it indicates an issue with other components of the circuit, such as a broken wire or a depleted power source.
Question- Why are standard symbols used in circuit diagrams important for understanding electrical circuits globally?
Answer- They provide a universal language for understanding and designing electrical circuits. Standardised symbols in circuit diagrams allow for a clear and concise representation of circuits, facilitating easy understanding and communication across different regions and languages.
Question- What is the primary difference in the output when electric cells are connected in series versus when they are connected in parallel?
Answer- Connecting in series increases the overall voltage, while connecting in parallel increases the capacity but maintains the same voltage as a single cell. In a series connection, the positive terminal of one cell is connected to the negative terminal of another, leading to a cumulative increase in voltage. In parallel connection, all positive terminals are connected together and all negative terminals are connected together, which increases the duration for which power is provided (capacity) but keeps the voltage the same as that of a single cell.
Question- Why would a copper wire not get as hot as a nichrome wire of the same length and thickness when the same amount of current is passed through both?
Answer- Because nichrome has a higher resistance than copper. The heating effect of electric current is influenced by the resistance of the wire. Nichrome, having higher resistance than copper, produces more heat for the same amount of current.
Question- What crucial role does an electric fuse play in household wiring?
Answer- It breaks the circuit by melting if too much current flows through it, preventing potential hazards like fire or appliance damage. An electric fuse contains a wire with a low melting point. When excessive current flows, the wire heats up, melts, and breaks the circuit, thereby stopping the flow of current and preventing hazards.
Question- Why is it not effective to connect the positive terminal of one electric cell to the positive terminal of another in creating a functional battery?
Answer- Such a setup does not create a proper path for current flow and fails to increase either voltage or capacity effectively. In a functional battery, the positive terminal of one cell must be connected to the negative terminal of another (series connection) to increase voltage, or all positives and negatives must be connected together (parallel connection) to increase capacity.
Question- What did Hans Christian Oersted discover about the relationship between electricity and magnetism?
Answer- He discovered that an electric current passing through a wire causes a nearby compass needle to deflect, linking electricity to magnetism. Oersted’s observation that an electric current can affect a compass needle was groundbreaking because it demonstrated for the first time that electricity and magnetism are related phenomena.
Question- How is the magnetic effect of an electric current enhanced when a wire is coiled?
Answer- The magnetic effect around the wire is increased with more turns in the coil. Coiling a wire carrying electric current amplifies the magnetic effect produced. The more turns in the coil, the stronger the magnetic effect becomes. This effect is further enhanced if the coil is wound around an iron core.
Question- How does lightning contribute to the creation of natural magnets like lodestones?
Answer- Lightning strikes can magnetise pieces of the mineral magnetite, creating natural magnets known as lodestones.The intense electrical energy and heat from lightning strikes can align the magnetic domains in magnetite, turning these pieces into naturally magnetised magnets, or lodestones.
Question- Why does an electric bulb produce light when current passes through its filament?
Answer- The filament gets extremely hot and starts to glow, producing light. Inside an electric bulb, the filament heats up due to the electric current’s heating effect. This intense heat makes the filament glow, thereby producing light.
Question- What is the main purpose of an electric fuse in electrical circuits?
Answer- To prevent excessive current flow and protect against potential hazards like fires or electrical damage. Electric fuses are safety devices that contain a material melting easily. When too much current flows through the circuit, the fuse wire melts, breaking the circuit and thus preventing overloading or short circuits.
Question- What makes Compact Fluorescent Lamps (CFLs) more energy-efficient compared to traditional incandescent bulbs?
Answer- CFLs convert more electricity into light and less into heat. Unlike traditional bulbs, which waste a significant portion of electricity in heat, CFLs efficiently convert electricity into light, resulting in less energy wastage and more efficiency.
Question- In the operation of an electric bell, what causes the armature to repeatedly strike the gong?
Answer- The continuous making and breaking of the circuit when the switch is pressed. When the electric bell’s switch is pressed, it completes the circuit, allowing the electromagnet to attract the armature. This movement breaks the circuit, causing the electromagnet to lose its magnetism and the spring to pull the armature back, which then completes the circuit again. This process repeats as long as the switch is pressed, causing continuous ringing.
Question- What role does the magnetization of the electromagnet play in the working of an electric bell?
Answer- It attracts the iron armature, initiating the process that leads to the ringing of the bell. The electromagnet in an electric bell, when magnetised by the electric current, attracts the iron armature towards itself. This movement of the armature towards the electromagnet and then away, due to the breaking and remaking of the circuit, leads to the clapper striking the gong and producing sound.
Question- How does the ability to control the magnetism of an electromagnet differ from that of a permanent magnet?
Answer- The magnetism of an electromagnet can be easily turned on or off by controlling the electric current, which is not possible with permanent magnets. Electromagnets are versatile in that their magnetic field can be controlled—activated or deactivated—by simply switching the electric current on or off. This is a significant contrast to permanent magnets, which maintain a constant magnetic field that cannot be easily altered.
Question- What are the main hazards associated with overloading in household wiring?
Answer- Overloading can heat the wires to very high temperatures, potentially causing fires. When too many electrical appliances are connected to a single socket, it draws a large amount of current, leading to overloading. This can cause the wires to overheat to dangerous levels, increasing the risk of fire hazards.
Question- How do Miniature Circuit Breakers (MCBs) differ in operation from traditional fuses?
Answer- MCBs operate on the magnetic effect of electric current and can be reset, unlike fuses which work on the heating effect and need to be replaced once they melt. MCBs automatically turn off when the current in a circuit exceeds a safe limit, a feature based on the magnetic effect of current. They are more convenient than fuses because they can be easily reset and reused, whereas fuses, which operate based on the heating effect of electric current, melt and need to be replaced when tripped.
Question- Why is the ISI mark significant for electrical appliances?
Answer- It indicates that the appliance meets the safety and quality standards set by the Indian Standards Institute. The ISI mark on an electrical appliance is a certification of its safety, quality, and efficiency in electricity usage. Appliances without this mark may not meet the necessary standards and could pose safety risks. This mark is therefore an important factor to consider when purchasing electrical appliances.
Very Short Answer Questions
Question- What happens in a closed circuit?
Answer-In a closed circuit, the switch is in the ON position, completing the path for electricity to flow, which allows the current to flow and the bulb to light up.
Question- What does a broken filament in a bulb signify in a circuit diagram?
Answer-
A broken filament in a bulb signifies an interrupted flow of electricity, often indicated by a broken or incomplete connection in a circuit diagram, resulting in the bulb not lighting up even if the switch is ON.
Question- What is the typical voltage provided by a single electric cell?
Answer- About 1.5 volts.
Question- What kind of battery is commonly used in cars?
Answer- Rechargeable batteries.
Question- Who discovered the magnetic effect of electric current?
Answer- Hans Christian Oersted.
Question- What happens to the magnetic effect when a current-carrying wire is coiled?
Answer-The magnetic effect is increased.
Question- What phenomenon results from the separation of charges during a thunderstorm?
Answer- Lightning.
Question- What is the primary function of a filament in an electric bulb?
Answer-To glow and produce light.
Question- What does a fuse do when excessive current flows through an electrical circuit?
Answer-It melts and breaks the circuit.
Question- In an electric bell, what part moves to strike the gong?
Answer- The clapper.
Question- What is an electromagnet?
Answer- An electromagnet is a magnet where the magnetic field is produced by an electric current.
Question- What happens in a short circuit?
Answer- A short circuit occurs when live and neutral wires come into direct contact, causing a large current to flow dangerously.
Question- What is the primary function of a fuse in an electrical circuit?
Answer- To stop the flow of excessive current and prevent potential fires and appliance damage.
Question- What does the ISI mark on an electrical appliance indicate?
Answer- It indicates that the appliance conforms to the safety and quality standards set by the Indian Standards Institute.
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