- A. switch L only
- B. switch M only
- C. Switch M and N only
- D. either switch L or switches M and N
(d) either switch L or switches M and N
- A. 2.5 mA
- B. 25 mA
- C. 250 mA
- D. 2500 mA
(c) 250 mA
False. Electron flow is in the opposite direction to conventional current flow. Electrons, being negatively charged particles, move from the negative terminal to the positive terminal of a cell or power source. However, conventional current is defined as the flow of positive charge, which is considered to move from the positive terminal to the negative terminal. This opposite direction between electron flow and conventional current flow is an important distinction in understanding electrical circuits and was established by convention before the discovery of electrons.
False. The fuse wire melts whenever there is overload in the wiring. A fuse is a safety device designed to protect electrical circuits from damage caused by excessive current. When the current flowing through the circuit exceeds the rated capacity of the fuse wire, the wire becomes very hot due to the heat effect of electric current and melts, breaking the circuit and stopping the flow of electricity. This prevents damage to appliances and reduces the risk of fire hazards in household wiring.
True. In a parallel circuit, the electric components are divided into branches. Each component is connected in a separate branch between the same two points, so each device has its own complete path for current flow. This arrangement allows each component to operate independently, and if one component fails or is switched off, the others continue to function normally. The total current from the source splits among the different branches.
False. The representation of the electric current is I. The symbol I is used to denote electric current in all electrical equations and circuit diagrams. Electric current is measured in amperes (A), where ampere is the unit of current, but the symbol representing current itself is the capital letter I. This standard notation is used universally in physics and electrical engineering.
True. The electrical conductivity of the semiconductor is in between a conductor and an insulator. Semiconductors are materials that have conductivity values that fall between good conductors like copper and silver, and insulators like rubber and glass. This intermediate conductivity makes semiconductors useful in electronic devices because their electrical properties can be modified and controlled by adding impurities or applying external voltages. Common examples of semiconductors include silicon and germanium.
A cell is a device that converts chemical energy into electrical energy, providing a source of power for circuits. A switch is a component used to open or close an electrical circuit, thereby controlling the flow of current. A circuit is defined as a complete and closed path through which electric current can flow. A Miniature Circuit Breaker (MCB) is a safety device that automatically interrupts the flow of current in a circuit when it detects an overload or short circuit; it can be reset by hand to restore the circuit. A fuse is also a safety device, designed to protect electrical circuits from damage due to overcurrent or short circuits by melting and breaking the circuit when the current exceeds a safe level.
wire
insulator
ammeter
10-6A
- A. Both A and R are true and R is the correct explanation of A.
- B. Both A and R are true but R is NOT the correct explanation of A.
- C. A is true but R is false.
- D. A is false but R is true.
A. Both A and R are true and R is the correct explanation of A
- A. If both A and R are true and the R is correct explanation of A.
- B. If both A and R are true but R is not a correct explanation of A.
- C. If A is true and R is false.
- D. If both A and R are false.
A. If both A and R are true and the R is correct explanation of A
Current travels at the speed of 1/100th times the speed of light 0.0002 m/s.
The SI unit of electrical conductivity is Siemens / metres (s/m).
The device used to generate electricity is an electric cell. An electric cell converts chemical energy into electrical energy through a chemical reaction inside it. It has two terminals, a positive terminal and a negative terminal, which create a potential difference that drives the flow of electrons through an external circuit. Electric cells are commonly used in flashlights, remote controls, and other portable electronic devices.
An electric fuse is a safety device which is used in household wiring and in many appliances to protect electrical circuits from damage caused by excessive current. It consists of a wire made of a material with a low melting point. When the current flowing through the circuit exceeds the rated capacity of the fuse, the wire becomes very hot and melts, breaking the circuit and stopping the flow of electricity. This prevents damage to appliances and reduces the risk of electrical fires in homes.
Some devices that run using the heat effect of electric current are electric bulb, which produces light and heat when current passes through its filament; geyser or electric water heater, which heats water for domestic use; and iron box, which generates heat to press clothes. Other examples include electric heater, toaster, and electric kettle. All these devices convert electrical energy into heat energy through the resistance of the wire or filament when electric current flows through them.
Some insulators are rubber, wood, plastic, and glass. Insulators are materials that do not allow electric current to flow through them easily because they have very few free electrons. Other common insulators include paper, cloth, ceramic, and air. These materials are used to cover conducting wires and to prevent unwanted flow of electric current, thereby providing safety in electrical circuits and appliances.
An electric current is the flow of electric charge through a conductor. It is measured by the amount of electric charge moving per unit time at any point in the circuit. Mathematically, electric current is defined as I equals Q divided by t, where I is the current, Q is the charge in coulombs, and t is the time in seconds. The conventional symbol for current is I, and it is measured in amperes (A). One ampere is defined as one coulomb of charge flowing past a point in one second. Electric current can flow in two directions: conventional current flows from the positive terminal to the negative terminal, while electron flow is in the opposite direction.
Parallel and series circuits differ in their structure, voltage distribution, current flow, and behavior when a component fails. In a parallel circuit, components are connected in separate branches that provide multiple paths for current flow. The voltage across each component remains the same and equals the voltage of the power source. Each bulb receives the full voltage and operates at full brightness. If one bulb burns out or is removed, the other bulbs continue to glow because current can still flow through the other branches. In contrast, a series circuit consists of a single loop where all components are connected one after another in a line. The current remains the same throughout all parts of the circuit as there is only one path for current flow. The voltage is divided among the components, so each bulb shares the total voltage of the power source and glows dimly. If one bulb burns out or is removed, the entire circuit is broken and all bulbs go out because there is no alternative path for current to flow. Therefore, parallel circuits are more practical for household use while series circuits are simpler but less reliable.
Electrical conductivity, also known as specific conductance, is the measure of a material's ability to conduct an electric current. It indicates how easily electrons can flow through a substance when an electric potential is applied. Materials with high electrical conductivity, such as copper and aluminum, allow electric current to pass through them readily and are called good conductors. Materials with low electrical conductivity, such as rubber and plastic, resist the flow of electric current and are called poor conductors or insulators. The electrical conductivity of a material depends on the number of free electrons available and how easily they can move through the material's structure.
A telephone works based on the principle of electromagnetic induction and the vibration of a diaphragm. The earpiece of a telephone contains a thin sheet of metal called a diaphragm that is made of a material that can be attracted to magnets. The diaphragm is attached to a spring that is fixed to the earpiece structure. When an electric current flows through the wires connected to the earpiece, a soft-iron bar inside becomes an electromagnet. This electromagnet attracts the metal diaphragm, pulling it inward. As the person on the other end of the line speaks, their voice causes variations in the electric current flowing through the circuit. These changing currents cause the electromagnet to become stronger and weaker alternately. As the strength of the electromagnet changes, the diaphragm is pulled in and pushed out repeatedly, causing it to vibrate. These vibrations of the diaphragm produce sound waves that we hear as the voice of the person speaking on the other end. The pattern of vibrations matches the pattern of the original voice, allowing us to understand what the other person is saying.
When an electric current passes through a wire or any conductor, the electrical energy is converted into heat energy. This phenomenon is called the heating effect of electric current. In heating appliances, the heating element is made of materials with high melting points that can withstand high temperatures without melting. Nichrome, an alloy composed of nickel, iron, and chromium, is a commonly used material for heating elements because of its high resistance and high melting point. When current flows through these materials, they become very hot and glow or produce heat. The heating effect of electric current has many practical applications in our daily life. Electric bulbs produce light and heat using this effect. Geysers heat water for bathing using heating coils. Electric iron boxes use heating elements to press clothes. Immersible water heaters heat water for domestic use. All these appliances contain heating coils made of materials with high resistance. The amount of heat produced depends on the resistance of the wire and the magnitude of the current flowing through it. Generation of heat due to electric current is known as the heating effect of electricity and is utilized in many useful ways.
A dry cell is a portable form of a leclanche cell.
It consists of zinc vessel which acts as a negative electrode or anode.
The vessel contains a moist paste of saw dust saturated with a solution of ammonium chloride an chloride.
The ammonium chloride acts as an electrolyte.
The purpose of zinc pide is to maintain the moistness of the paste being highly gyroscopic.
The carbon rod covered with a brass cap is placed in the middle of the vessel. It acts as positive electrode or cathode.
It is surrounded by a closely packed mixture of charcoal and manganese dioxide (Mn0 2 ) in a muslin bag.
Here Mn0 2 acts as depolarizer. The zinc vessel is sealed at the top with pitch or shellac.
A small hole is provided in it to allow the gases formed by the chemical action to escape.
The chemical action inside the cell is the same as in avalanche cell.
Even when a circuit appears to be complete and the switch is in the ON position, a torch bulb may not glow due to several possible reasons. The cell or battery may be completely discharged and unable to provide electrical energy to the circuit. The bulb filament may be fused or broken, preventing current from flowing through it and producing light. The wire in the circuit may be broken from inside, which is not visible from outside, interrupting the flow of current even though the circuit looks complete. The connections between the wires, battery terminals, and bulb may be loose, creating a gap that prevents current from flowing smoothly through the circuit. Any of these issues would break the circuit or prevent the flow of current, resulting in the bulb not glowing despite the circuit appearing to be properly connected.
- A. SI, S2 and S4 only
- B. SI, S3 and S5 only
- C. S2, S3 and S4 only
- D. S2, S3 and S5 only
(c) S2, S3 and S4 only
- A. A only
- B. C only
- C. A and B only
- D. A, B and C
(c) A and B only
If someone is exhausted and about to faint, the appropriate first aid is to help them rest and recover their energy. You should make them lie down in a comfortable position with their legs elevated to improve blood circulation to the brain. Provide them with water to drink to help them rehydrate. Loosen any tight clothing that might restrict breathing. Ensure they are in a cool, well-ventilated area. Allow them to rest for some time until they feel better. If the person loses consciousness or does not recover after resting, seek medical help immediately.