G11 T3 Classwork 5 And 6

1. What is the symbol for a fuse?

The symbol for a fuse is represented by the letter "B" or "b". This symbol is commonly used in electrical circuit diagrams to indicate the presence of a fuse, which is a safety device that protects the circuit from overcurrent. The lowercase "b" is often used to represent a fuse that is built into a circuit, while the uppercase "B" is used for a fuse that is external to the circuit.

Explanation

The symbol for a fuse is represented by the letter "B" or "b". This symbol is commonly used in electrical circuit diagrams to indicate the presence of a fuse, which is a safety device that protects the circuit from overcurrent. The lowercase "b" is often used to represent a fuse that is built into a circuit, while the uppercase "B" is used for a fuse that is external to the circuit.

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2. Resistors R3 and R4 are connected in:

The resistors R3 and R4 are connected in parallel. This means that both resistors are connected to the same two points in the circuit, creating multiple paths for the current to flow. In a parallel connection, the voltage across each resistor is the same, while the total current is divided between the resistors. This allows for different amounts of resistance to be present in the circuit, providing different paths for the current to take.

Explanation

The resistors R3 and R4 are connected in parallel. This means that both resistors are connected to the same two points in the circuit, creating multiple paths for the current to flow. In a parallel connection, the voltage across each resistor is the same, while the total current is divided between the resistors. This allows for different amounts of resistance to be present in the circuit, providing different paths for the current to take.

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3. Calculate the potential difference (p.d.) across the 200 Ω resistor if the current passing through it is 0.025 A.

The potential difference (p.d.) across a resistor can be calculated using Ohm's Law, which states that V = I * R, where V is the potential difference, I is the current, and R is the resistance. In this case, the current passing through the 200 Ω resistor is given as 0.025 A. Therefore, the potential difference across the resistor can be calculated as V = 0.025 A * 200 Ω = 5 V.

Explanation

The potential difference (p.d.) across a resistor can be calculated using Ohm's Law, which states that V = I * R, where V is the potential difference, I is the current, and R is the resistance. In this case, the current passing through the 200 Ω resistor is given as 0.025 A. Therefore, the potential difference across the resistor can be calculated as V = 0.025 A * 200 Ω = 5 V.

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4. In the circuit below, X and Y are identical 6 V lamps.

What happens when the switch is closed?

X lights more brightly than Y.

Y lights more brightly than X.

X and Y light with equal brightness.

Neither X nor Y light.

When the switch is closed, the current flows through both lamps X and Y in the circuit. Since X and Y are identical 6 V lamps, they have the same resistance. Therefore, the current passing through both lamps will be the same, causing them to light up with equal brightness.

Explanation

When the switch is closed, the current flows through both lamps X and Y in the circuit. Since X and Y are identical 6 V lamps, they have the same resistance. Therefore, the current passing through both lamps will be the same, causing them to light up with equal brightness.

5. Two faulty ammeters and two perfect ammeters are connected in series in the circuit shown.

The readings on the ammeters are:A₁ 2.9 AA₂ 3.1 AA₃ 3.1 AA₄ 3.3 AWhich two ammeters are faulty?

A1 and A2

A1 and A4

A2 and A3

A3 and A4

The two faulty ammeters can be identified by comparing their readings with the readings of the perfect ammeters. In this case, A1 and A4 have readings of 2.9 A and 3.3 A respectively, while the perfect ammeters have readings of 3.1 A. Since A1 and A4 have readings that are significantly different from the perfect ammeters, it can be concluded that A1 and A4 are faulty.

Explanation

The two faulty ammeters can be identified by comparing their readings with the readings of the perfect ammeters. In this case, A1 and A4 have readings of 2.9 A and 3.3 A respectively, while the perfect ammeters have readings of 3.1 A. Since A1 and A4 have readings that are significantly different from the perfect ammeters, it can be concluded that A1 and A4 are faulty.

6. A cruise ship is anchored in a harbour. The crew holds a party for the guests on board, and the
ship's electrical department decorates the decks with strings of coloured lamps.

Each string of lamps contains thirty 100 V lamps. The strings of lamps are run from a 100 Vgenerator. The resistance of each lamp is 250 Ω. Ignore the resistance of the generator.Calculate the current in each lamp when it is at normal brightness.

Each lamp has a resistance of 250 Ω and is connected in series with other lamps in a string. Since the lamps are connected in series, the current passing through each lamp is the same.

Using Ohm's Law (V = IR), we can calculate the current in each lamp. The voltage across each lamp is 100 V and the resistance is 250 Ω.

I = V / R
I = 100 V / 250 Ω
I = 0.4 A

Therefore, the current in each lamp when it is at normal brightness is 0.4 A.

Explanation

Each lamp has a resistance of 250 Ω and is connected in series with other lamps in a string. Since the lamps are connected in series, the current passing through each lamp is the same.

Using Ohm's Law (V = IR), we can calculate the current in each lamp. The voltage across each lamp is 100 V and the resistance is 250 Ω.

I = V / R
I = 100 V / 250 Ω
I = 0.4 A

Therefore, the current in each lamp when it is at normal brightness is 0.4 A.

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7. Which statement is correct?

A fuse is included in a circuit to prevent the current becoming too high.

A fuse should be connected to the neutral wire in a plug.

An electric circuit will only work if it includes a fuse.

An earth wire is needed to prevent the fuse blowing.

A fuse is included in a circuit to prevent the current from becoming too high. This is because a fuse is designed to break the circuit when the current exceeds a certain limit, thereby protecting the circuit and the connected devices from damage caused by excessive current. By breaking the circuit, the fuse prevents the flow of current and avoids overheating, fire, or other hazards that can occur when the current becomes too high.

Explanation

A fuse is included in a circuit to prevent the current from becoming too high. This is because a fuse is designed to break the circuit when the current exceeds a certain limit, thereby protecting the circuit and the connected devices from damage caused by excessive current. By breaking the circuit, the fuse prevents the flow of current and avoids overheating, fire, or other hazards that can occur when the current becomes too high.

8. The circuit shown contains four lamps and three switches

Which switches must be closed to light only lamps 1 and 3?

Switch 1 only

Switch 1 and switch 2 only

Switch 1 and switch 3 only

Switch 2 and switch 3 only

To light only lamps 1 and 3, we need to close the switches that are connected to these lamps. Switch 1 is connected to lamp 1, so closing switch 1 will light lamp 1. Switch 3 is connected to lamp 3, so closing switch 3 will light lamp 3. Closing switch 2 will not affect lamps 1 and 3 as it is not connected to either of them. Therefore, the correct answer is Switch 1 only.

Explanation

To light only lamps 1 and 3, we need to close the switches that are connected to these lamps. Switch 1 is connected to lamp 1, so closing switch 1 will light lamp 1. Switch 3 is connected to lamp 3, so closing switch 3 will light lamp 3. Closing switch 2 will not affect lamps 1 and 3 as it is not connected to either of them. Therefore, the correct answer is Switch 1 only.

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10. An electric power tool is being used outdoors in a shower of rain.What is the greatest hazard to the user?

The cable gets hot and causes burns.

The circuit-breaker cuts off the current.

The current passes through water and causes a shock.

The tool rusts.

The greatest hazard to the user when using an electric power tool outdoors in a shower of rain is the current passing through water and causing a shock. Water is a conductor of electricity, and when it comes into contact with the power tool, it can create a pathway for the electric current to flow through the user's body, resulting in an electric shock. This can be extremely dangerous and potentially life-threatening. It is important to avoid using electric power tools in wet conditions to prevent this hazard.

Explanation

The greatest hazard to the user when using an electric power tool outdoors in a shower of rain is the current passing through water and causing a shock. Water is a conductor of electricity, and when it comes into contact with the power tool, it can create a pathway for the electric current to flow through the user's body, resulting in an electric shock. This can be extremely dangerous and potentially life-threatening. It is important to avoid using electric power tools in wet conditions to prevent this hazard.

11. A cable in a house is carrying too much current.What is the greatest danger?

Appliances not working

Electric shock

Fire

Low power

When a cable in a house carries too much current, it can lead to an overload situation. This can cause the insulation of the cable to deteriorate and potentially result in a short circuit. If someone comes into contact with the exposed wiring, they may receive an electric shock, which can be extremely dangerous and even fatal. Therefore, the greatest danger when a cable is carrying too much current is the risk of electric shock.

Explanation

When a cable in a house carries too much current, it can lead to an overload situation. This can cause the insulation of the cable to deteriorate and potentially result in a short circuit. If someone comes into contact with the exposed wiring, they may receive an electric shock, which can be extremely dangerous and even fatal. Therefore, the greatest danger when a cable is carrying too much current is the risk of electric shock.

12. A cruise ship is anchored in a harbour. The crew holds a party for the guests on board, and theship's electrical department decorates the decks with strings of coloured lamps.

Each string of lamps contains thirty 100 V lamps. The strings of lamps are run from a 100 Vgenerator. The resistance of each lamp is 250 Ω. Ignore the resistance of the generator.State whether the lamps on a particular string are connected in series or in parallel.

Series

Parallel

The lamps on a particular string are connected in parallel because in a parallel circuit, the components are connected in such a way that the current has multiple paths to flow through. In this case, each lamp is connected directly to the generator, allowing the current to flow independently through each lamp. If the lamps were connected in series, the current would have to flow through each lamp in sequence, which would result in a decrease in brightness as more lamps are added to the string.

Explanation

The lamps on a particular string are connected in parallel because in a parallel circuit, the components are connected in such a way that the current has multiple paths to flow through. In this case, each lamp is connected directly to the generator, allowing the current to flow independently through each lamp. If the lamps were connected in series, the current would have to flow through each lamp in sequence, which would result in a decrease in brightness as more lamps are added to the string.

13. A student makes the circuit shown.

The fuse has blown and stopped the current.What could have caused this?

The current rating of the fuse was too high.

The current was too large.

The lamp was loose.

The voltage was too small.

The correct answer is "The current was too large." This means that the amount of current flowing through the circuit exceeded the maximum limit that the fuse could handle. When the current exceeds this limit, the fuse blows to prevent any damage or danger.

Explanation

The correct answer is "The current was too large." This means that the amount of current flowing through the circuit exceeded the maximum limit that the fuse could handle. When the current exceeds this limit, the fuse blows to prevent any damage or danger.

14. Why is a fuse used in an electrical circuit in a house?

To increase the circuit resistance

To keep the power used to a minimum value

To prevent a short-circuit from occurring

To stop the cables from carrying too much current

A fuse is used in an electrical circuit in a house to stop the cables from carrying too much current. When the current flowing through the circuit exceeds a safe limit, the fuse will melt and break the circuit, preventing further flow of current. This helps to protect the electrical appliances and wiring from damage due to excessive current.

Explanation

A fuse is used in an electrical circuit in a house to stop the cables from carrying too much current. When the current flowing through the circuit exceeds a safe limit, the fuse will melt and break the circuit, preventing further flow of current. This helps to protect the electrical appliances and wiring from damage due to excessive current.

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16. A lamp is to be connected in a circuit so that the p.d. across it can be varied from 0 to 6 V.Which circuit would be most suitable?

Circuit b,B would be most suitable because it allows the potential difference (p.d.) across the lamp to be varied from 0 to 6 V. The symbol "b" typically represents a variable resistor or potentiometer, which can be adjusted to change the resistance in the circuit. This, in turn, can control the current flowing through the lamp and hence the p.d. across it. By adjusting the resistance, the p.d. across the lamp can be varied within the desired range of 0 to 6 V.

Explanation

Circuit b,B would be most suitable because it allows the potential difference (p.d.) across the lamp to be varied from 0 to 6 V. The symbol "b" typically represents a variable resistor or potentiometer, which can be adjusted to change the resistance in the circuit. This, in turn, can control the current flowing through the lamp and hence the p.d. across it. By adjusting the resistance, the p.d. across the lamp can be varied within the desired range of 0 to 6 V.

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17. Which circuit is a variable potential divider (potentiometer)?

The correct answer is b,B. A potentiometer is a type of variable resistor that can be used as a voltage divider. It consists of a resistive element and a sliding contact, which can be moved along the resistive element to vary the output voltage. In this case, the circuit represented by b and B shows a potentiometer with the resistive element and the sliding contact, making it the correct answer.

Explanation

The correct answer is b,B. A potentiometer is a type of variable resistor that can be used as a voltage divider. It consists of a resistive element and a sliding contact, which can be moved along the resistive element to vary the output voltage. In this case, the circuit represented by b and B shows a potentiometer with the resistive element and the sliding contact, making it the correct answer.

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18. We want to have two 6V lamps in the circuit with the 6 V supply.Which of the following means of connecting the lamps between X and Y is the best?

1, because they are in series, shine brighter and can be controlled independently.

1, because they are in parallel and shine brighter and can be controlled independently.

2, because they are in series and shine brighter and can be controlled independently.

2, because they are in parallel and shine brighter and can be controlled independently.

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Explanation

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19. The circuit contains a relay.

When switch S is closed, what is the state of the lamps?

Lamp 1 ON, lamp 2 ON

Lamp 1 ON, lamp 2 OFF

Lamp 1 OFF, lamp 2 ON

Lamp 1 OFF, lamp 2 OFF

When the switch S is closed, it completes the circuit and allows current to flow through the relay. The relay then switches on, closing the contacts and connecting both lamps to the power source. Therefore, both Lamp 1 and Lamp 2 will be turned on.

Explanation

When the switch S is closed, it completes the circuit and allows current to flow through the relay. The relay then switches on, closing the contacts and connecting both lamps to the power source. Therefore, both Lamp 1 and Lamp 2 will be turned on.

20. Four lamps and four switches are connected to a power supply as shown in the circuit diagram.When all the switches are closed, all the lamps are lit.When one of the switches is then opened, only one lamp goes out.Which switch is opened?

In the given circuit diagram, there are four lamps and four switches connected to a power supply. Initially, when all the switches are closed, all the lamps are lit. However, when one of the switches is opened, only one lamp goes out. From the information provided, it can be inferred that the switch which corresponds to the lamp that goes out when opened is switch d. Additionally, switch D is also opened as mentioned in the answer.

Explanation

In the given circuit diagram, there are four lamps and four switches connected to a power supply. Initially, when all the switches are closed, all the lamps are lit. However, when one of the switches is opened, only one lamp goes out. From the information provided, it can be inferred that the switch which corresponds to the lamp that goes out when opened is switch d. Additionally, switch D is also opened as mentioned in the answer.

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