Case Based Questions Test: Current Electricity - Grade 12 MCQ

Read the following text and answer the following questions on the basis of the same:

Shunt resistance: The ammeter shunt is the device which provides the low resistance path to the flow of current. It is connected in parallel with the ammeter. In some ammeter the shunt is in-built inside the instrument while in others it is externally connected to the circuit. Ammeters are designed for measurement of low current. For measuring high current, the shunt is connected in parallel to the ammeter. The significant portion of the current passes to the shunt because of the low resistance path and little amount of current passes through the ammeter. The shunt is connected in parallel to the ammeter because of which the voltage drops across the meter and shunt remain the same. Thus, the movement of the pointer is not affected by the shunt. Let us consider that the current to be measured is I. The circuit has ammeter and shunt connected parallel to each other. The ammeter is designed for measurement of small current say, Im. The magnitude of the current I passes through the meter is very high, and it will burn the meter. So, for measuring the current I the shunt is required in the circuit. As the shunt connects in parallel with the ammeter, thus the same voltage drops occur between them:

I_ShR_SH = I_mR_m

∴ R_SH = I_mR_m/I_SH

Shunt current I_SH = I – I_m

So, R_SH = I_mR_m/(I – I_m)

∴ I/I_m = 1 + (R_m/R_SH)

The ratio of the total current to the current required for the movement of the ammeter coil is called the multiplying power of the shunt.

∴ The multiplying power = m = I/Im

RSH = Rm / (m – 1)

The following are the requirements of the shunt.

• The resistance of the shunt should remain constant with time.

• The temperature of the material should remain the same even though substantial current flows through the circuit.

Manganin and Constantan are used for making the shunt of DC and AC ammeter respectively. What is multiplying power of the shunt?

Read the following text and answer the following questions on the basis of the same:

Shunt resistance: The ammeter shunt is the device which provides the low resistance path to the flow of current. It is connected in parallel with the ammeter. In some ammeter the shunt is in-built inside the instrument while in others it is externally connected to the circuit. Ammeters are designed for measurement of low current. For measuring high current, the shunt is connected in parallel to the ammeter. The significant portion of the current passes to the shunt because of the low resistance path and little amount of current passes through the ammeter. The shunt is connected in parallel to the ammeter because of which the voltage drops across the meter and shunt remain the same. Thus, the movement of the pointer is not affected by the shunt. Let us consider that the current to be measured is I. The circuit has ammeter and shunt connected parallel to each other. The ammeter is designed for measurement of small current say, Im. The magnitude of the current I passes through the meter is very high, and it will burn the meter. So, for measuring the current I the shunt is required in the circuit. As the shunt connects in parallel with the ammeter, thus the same voltage drops occur between them:

I_ShR_SH = I_mR_m

∴ R_SH = I_mR_m/I_SH

Shunt current I_SH = I – I_m

So, R_SH = I_mR_m/(I – I_m)

∴ I/I_m = 1 + (R_m/R_SH)

The ratio of the total current to the current required for the movement of the ammeter coil is called the multiplying power of the shunt.

∴ The multiplying power = m = I/Im

RSH = Rm / (m – 1)

The following are the requirements of the shunt.

• The resistance of the shunt should remain constant with time.

• The temperature of the material should remain the same even though substantial current flows through the circuit.

Current through shunt is

Read the following text and answer the following questions on the basis of the same:

Shunt resistance: The ammeter shunt is the device which provides the low resistance path to the flow of current. It is connected in parallel with the ammeter. In some ammeter the shunt is in-built inside the instrument while in others it is externally connected to the circuit. Ammeters are designed for measurement of low current. For measuring high current, the shunt is connected in parallel to the ammeter. The significant portion of the current passes to the shunt because of the low resistance path and little amount of current passes through the ammeter. The shunt is connected in parallel to the ammeter because of which the voltage drops across the meter and shunt remain the same. Thus, the movement of the pointer is not affected by the shunt. Let us consider that the current to be measured is I. The circuit has ammeter and shunt connected parallel to each other. The ammeter is designed for measurement of small current say, Im. The magnitude of the current I passes through the meter is very high, and it will burn the meter. So, for measuring the current I the shunt is required in the circuit. As the shunt connects in parallel with the ammeter, thus the same voltage drops occur between them:

I_ShR_SH = I_mR_m

∴ R_SH = I_mR_m/I_SH

Shunt current I_SH = I – I_m

So, R_SH = I_mR_m/(I – I_m)

∴ I/I_m = 1 + (R_m/R_SH)

The ratio of the total current to the current required for the movement of the ammeter coil is called the multiplying power of the shunt.

∴ The multiplying power = m = I/Im

RSH = Rm / (m – 1)

The following are the requirements of the shunt.

• The resistance of the shunt should remain constant with time.

• The temperature of the material should remain the same even though substantial current flows through the circuit.

What will be the value of the shunt resistance if the ammeter coil resistance is 1Ω and multiplying power is 100?

Read the following text and answer the following questions on the basis of the same:

Types of resistors Most common type of resistor is Carbon Composition Resistors. Carbon resistors are a cheap, general purpose resistor used in electrical and electronic circuits. Their resistive element is manufactured from a mixture of finely ground carbon dust or graphite and a non-conducting ceramic powder to bind it all together. The ratio of carbon dust to ceramic (conductor to insulator) determines the resistive value of the resistor. Higher the ratio of carbon, lower the overall resistance. Film Type Resistors consist of Metal Film, Carbon Film and Metal Oxide Film .Such resistors are generally made by depositing pure metals, such as nickel, or an oxide film, such as tin-oxide, on an insulating ceramic rod or substrate. The resistive value of the resistor is controlled by increasing the desired thickness of the deposited film giving them the names of either “thick-film resistors” or “thin-film resistors”. Film type resistors can achieve much higher ohmic value compared to other types. Another type of resistor, called a Wirewound Resistor, is made by winding a thin metal alloy wire (Nichrome) or similar wire on an insulating ceramic former in the form of a spiral helix. These types of resistors are generally only available in very low ohmic value with high precision . They are able to handle much higher electrical currents than other resistors of the same ohmic value with much excessive power ratings. These high power resistors are moulded into an aluminium heat sink body with fins attached to increase their overall surface area to promote heat loss and cooling.

Carbon composition resistors are made from a mixture of

Read the following text and answer the following questions on the basis of the same:

Types of resistors Most common type of resistor is Carbon Composition Resistors. Carbon resistors are a cheap, general purpose resistor used in electrical and electronic circuits. Their resistive element is manufactured from a mixture of finely ground carbon dust or graphite and a non-conducting ceramic powder to bind it all together. The ratio of carbon dust to ceramic (conductor to insulator) determines the resistive value of the resistor. Higher the ratio of carbon, lower the overall resistance. Film Type Resistors consist of Metal Film, Carbon Film and Metal Oxide Film .Such resistors are generally made by depositing pure metals, such as nickel, or an oxide film, such as tin-oxide, on an insulating ceramic rod or substrate. The resistive value of the resistor is controlled by increasing the desired thickness of the deposited film giving them the names of either “thick-film resistors” or “thin-film resistors”. Film type resistors can achieve much higher ohmic value compared to other types. Another type of resistor, called a Wirewound Resistor, is made by winding a thin metal alloy wire (Nichrome) or similar wire on an insulating ceramic former in the form of a spiral helix. These types of resistors are generally only available in very low ohmic value with high precision . They are able to handle much higher electrical currents than other resistors of the same ohmic value with much excessive power ratings. These high power resistors are moulded into an aluminium heat sink body with fins attached to increase their overall surface area to promote heat loss and cooling.

Metal Film Type Resistors are generally made by depositing pure ______, on ______ rod or substrate.

Read the following text and answer the following questions on the basis of the same:

Types of resistors Most common type of resistor is Carbon Composition Resistors. Carbon resistors are a cheap, general purpose resistor used in electrical and electronic circuits. Their resistive element is manufactured from a mixture of finely ground carbon dust or graphite and a non-conducting ceramic powder to bind it all together. The ratio of carbon dust to ceramic (conductor to insulator) determines the resistive value of the resistor. Higher the ratio of carbon, lower the overall resistance. Film Type Resistors consist of Metal Film, Carbon Film and Metal Oxide Film .Such resistors are generally made by depositing pure metals, such as nickel, or an oxide film, such as tin-oxide, on an insulating ceramic rod or substrate. The resistive value of the resistor is controlled by increasing the desired thickness of the deposited film giving them the names of either “thick-film resistors” or “thin-film resistors”. Film type resistors can achieve much higher ohmic value compared to other types. Another type of resistor, called a Wirewound Resistor, is made by winding a thin metal alloy wire (Nichrome) or similar wire on an insulating ceramic former in the form of a spiral helix. These types of resistors are generally only available in very low ohmic value with high precision . They are able to handle much higher electrical currents than other resistors of the same ohmic value with much excessive power ratings. These high power resistors are moulded into an aluminium heat sink body with fins attached to increase their overall surface area to promote heat loss and cooling.

Wire wound resistors are available in very ____ ohmic high precision values with ______ power rating.

Read the following text and answer the following questions on the basis of the same: Electric Toaster : Small Industries Service Institute Takyelpat Industrial Estate Imphal has designed an Electric toaster which is operated at 220 volts A.C., single phase and available in four different rated capacity such as 600 W, 750 W, 1000 W and 1250 W. The heating element is made of nichrome 80/20 (80% nickel, 20% chromium), since Nichrome does not get oxidise readily at high temperature and have higher resistivity, so it produces more heat. The element is wound separately on Mica sheets and fitted with body of toaster with the help of ceramic terminals.

What is meant by 80/20 Nichrome?

Read the following text and answer the following questions on the basis of the same: Electric Toaster : Small Industries Service Institute Takyelpat Industrial Estate Imphal has designed an Electric toaster which is operated at 220 volts A.C., single phase and available in four different rated capacity such as 600 W, 750 W, 1000 W and 1250 W. The heating element is made of nichrome 80/20 (80% nickel, 20% chromium), since Nichrome does not get oxidise readily at high temperature and have higher resistivity, so it produces more heat. The element is wound separately on Mica sheets and fitted with body of toaster with the help of ceramic terminals.

Operating voltage of the device is:

Read the following text and answer the following questions on the basis of the same:

Shunt resistance: The ammeter shunt is the device which provides the low resistance path to the flow of current. It is connected in parallel with the ammeter. In some ammeter the shunt is in-built inside the instrument while in others it is externally connected to the circuit. Ammeters are designed for measurement of low current. For measuring high current, the shunt is connected in parallel to the ammeter. The significant portion of the current passes to the shunt because of the low resistance path and little amount of current passes through the ammeter. The shunt is connected in parallel to the ammeter because of which the voltage drops across the meter and shunt remain the same. Thus, the movement of the pointer is not affected by the shunt. Let us consider that the current to be measured is I. The circuit has ammeter and shunt connected parallel to each other. The ammeter is designed for measurement of small current say, Im. The magnitude of the current I passes through the meter is very high, and it will burn the meter. So, for measuring the current I the shunt is required in the circuit. As the shunt connects in parallel with the ammeter, thus the same voltage drops occur between them:

I_ShR_SH = I_mR_m

∴ R_SH = I_mR_m/I_SH

Shunt current I_SH = I – I_m

So, R_SH = I_mR_m/(I – I_m)

∴ I/I_m = 1 + (R_m/R_SH)

The ratio of the total current to the current required for the movement of the ammeter coil is called the multiplying power of the shunt.

∴ The multiplying power = m = I/Im

RSH = Rm / (m – 1)

The following are the requirements of the shunt.

• The resistance of the shunt should remain constant with time.

• The temperature of the material should remain the same even though substantial current flows through the circuit.

Materials used for making shunt of DC and AC ammeter are respectively

Read the following text and answer the following questions on the basis of the same:

Shunt resistance: The ammeter shunt is the device which provides the low resistance path to the flow of current. It is connected in parallel with the ammeter. In some ammeter the shunt is in-built inside the instrument while in others it is externally connected to the circuit. Ammeters are designed for measurement of low current. For measuring high current, the shunt is connected in parallel to the ammeter. The significant portion of the current passes to the shunt because of the low resistance path and little amount of current passes through the ammeter. The shunt is connected in parallel to the ammeter because of which the voltage drops across the meter and shunt remain the same. Thus, the movement of the pointer is not affected by the shunt. Let us consider that the current to be measured is I. The circuit has ammeter and shunt connected parallel to each other. The ammeter is designed for measurement of small current say, Im. The magnitude of the current I passes through the meter is very high, and it will burn the meter. So, for measuring the current I the shunt is required in the circuit. As the shunt connects in parallel with the ammeter, thus the same voltage drops occur between them:

I_ShR_SH = I_mR_m

∴ R_SH = I_mR_m/I_SH

Shunt current I_SH = I – I_m

So, R_SH = I_mR_m/(I – I_m)

∴ I/I_m = 1 + (R_m/R_SH)

The ratio of the total current to the current required for the movement of the ammeter coil is called the multiplying power of the shunt.

∴ The multiplying power = m = I/Im

RSH = Rm / (m – 1)

The following are the requirements of the shunt.

• The resistance of the shunt should remain constant with time.

• The temperature of the material should remain the same even though substantial current flows through the circuit.

How shunt is connected with a ammeter?

Read the following text and answer the following questions on the basis of the same:

Types of resistors Most common type of resistor is Carbon Composition Resistors. Carbon resistors are a cheap, general purpose resistor used in electrical and electronic circuits. Their resistive element is manufactured from a mixture of finely ground carbon dust or graphite and a non-conducting ceramic powder to bind it all together. The ratio of carbon dust to ceramic (conductor to insulator) determines the resistive value of the resistor. Higher the ratio of carbon, lower the overall resistance. Film Type Resistors consist of Metal Film, Carbon Film and Metal Oxide Film .Such resistors are generally made by depositing pure metals, such as nickel, or an oxide film, such as tin-oxide, on an insulating ceramic rod or substrate. The resistive value of the resistor is controlled by increasing the desired thickness of the deposited film giving them the names of either “thick-film resistors” or “thin-film resistors”. Film type resistors can achieve much higher ohmic value compared to other types. Another type of resistor, called a Wirewound Resistor, is made by winding a thin metal alloy wire (Nichrome) or similar wire on an insulating ceramic former in the form of a spiral helix. These types of resistors are generally only available in very low ohmic value with high precision . They are able to handle much higher electrical currents than other resistors of the same ohmic value with much excessive power ratings. These high power resistors are moulded into an aluminium heat sink body with fins attached to increase their overall surface area to promote heat loss and cooling.

In carbon composition resistors, ______ the ratio of carbon, _____ the overall resistance.

Read the following text and answer the following questions on the basis of the same:

Types of resistors Most common type of resistor is Carbon Composition Resistors. Carbon resistors are a cheap, general purpose resistor used in electrical and electronic circuits. Their resistive element is manufactured from a mixture of finely ground carbon dust or graphite and a non-conducting ceramic powder to bind it all together. The ratio of carbon dust to ceramic (conductor to insulator) determines the resistive value of the resistor. Higher the ratio of carbon, lower the overall resistance. Film Type Resistors consist of Metal Film, Carbon Film and Metal Oxide Film .Such resistors are generally made by depositing pure metals, such as nickel, or an oxide film, such as tin-oxide, on an insulating ceramic rod or substrate. The resistive value of the resistor is controlled by increasing the desired thickness of the deposited film giving them the names of either “thick-film resistors” or “thin-film resistors”. Film type resistors can achieve much higher ohmic value compared to other types. Another type of resistor, called a Wirewound Resistor, is made by winding a thin metal alloy wire (Nichrome) or similar wire on an insulating ceramic former in the form of a spiral helix. These types of resistors are generally only available in very low ohmic value with high precision . They are able to handle much higher electrical currents than other resistors of the same ohmic value with much excessive power ratings. These high power resistors are moulded into an aluminium heat sink body with fins attached to increase their overall surface area to promote heat loss and cooling.

Wirewound Resistors are made by winding a thin _____ or similar wire on an ____ former in the form of a spiral helix.