5.1.5 - 5.1.10 Electric Circuits

1. 100mA is enough to kill a person. If a man's electrical resistance is around 1000 ohms when he gets out of the shower, what voltage would just be enough to kill him?

1V

10V

100V

240V

The voltage required to kill a person can be calculated using Ohm's Law, which states that voltage is equal to current multiplied by resistance. In this case, the resistance is given as 1000 ohms and the current required to kill a person is stated as 100mA. Rearranging the formula, we can determine that voltage is equal to current divided by resistance. Therefore, the voltage required to kill a person with a resistance of 1000 ohms is 100V.

Explanation

The voltage required to kill a person can be calculated using Ohm's Law, which states that voltage is equal to current multiplied by resistance. In this case, the resistance is given as 1000 ohms and the current required to kill a person is stated as 100mA. Rearranging the formula, we can determine that voltage is equal to current divided by resistance. Therefore, the voltage required to kill a person with a resistance of 1000 ohms is 100V.

2. What is the power required by a 4amp 240 V applicance?

0.0166666 W

60W

960W

6KW

The power required by an appliance can be calculated using the formula P = IV, where P is power, I is current, and V is voltage. In this case, the current is given as 4 amps and the voltage is given as 240 volts. Plugging these values into the formula, we get P = 4 amps * 240 volts = 960 watts. Therefore, the correct answer is 960W.

Explanation

The power required by an appliance can be calculated using the formula P = IV, where P is power, I is current, and V is voltage. In this case, the current is given as 4 amps and the voltage is given as 240 volts. Plugging these values into the formula, we get P = 4 amps * 240 volts = 960 watts. Therefore, the correct answer is 960W.

3. How would you describe the I/V graph of a filament lamp (I - y axis, V - x axis)?

Straight line graph through the origin

Straight line graph through the origin but starts to curve slightly up at end

Straight line graph through the origin but starts to curve slightly down at end

Straight line graph through the origin then horizontal line

Straight line graph through the origin then a vertical line

The I/V graph of a filament lamp is a straight line graph through the origin but starts to curve slightly down at the end. This is because the resistance of the filament increases as the temperature of the lamp increases. As the current through the lamp increases, the temperature of the filament also increases, causing the resistance to increase. This leads to a decrease in the voltage across the lamp for a given current, resulting in the graph curving slightly downwards at the end.

Explanation

The I/V graph of a filament lamp is a straight line graph through the origin but starts to curve slightly down at the end. This is because the resistance of the filament increases as the temperature of the lamp increases. As the current through the lamp increases, the temperature of the filament also increases, causing the resistance to increase. This leads to a decrease in the voltage across the lamp for a given current, resulting in the graph curving slightly downwards at the end.

4. How would you double the resistance of a piece of wire?

Warm it up

Half its length

Double its width

Double its length

Double its length AND half its width

By doubling the length of a wire, its resistance will also double. This is because resistance is directly proportional to the length of the wire. Increasing the length of the wire will result in more collisions between the electrons and the atoms in the wire, which in turn increases resistance. Therefore, doubling the length of the wire will effectively double its resistance.

Explanation

By doubling the length of a wire, its resistance will also double. This is because resistance is directly proportional to the length of the wire. Increasing the length of the wire will result in more collisions between the electrons and the atoms in the wire, which in turn increases resistance. Therefore, doubling the length of the wire will effectively double its resistance.

5. What does the resistivity of a resistor depend on?

Its length

Its width

Its length and its width

Its mass

The material it is made of

The resistivity of a resistor depends on the material it is made of. Different materials have different resistivities, which determine how well they can resist the flow of electric current. Resistivity is a fundamental property of a material and is independent of the dimensions of the resistor such as length or width. The resistivity value of a material is used to calculate the resistance of a resistor using the formula R = ρL/A, where ρ is the resistivity, L is the length of the resistor, and A is the cross-sectional area.

Explanation

The resistivity of a resistor depends on the material it is made of. Different materials have different resistivities, which determine how well they can resist the flow of electric current. Resistivity is a fundamental property of a material and is independent of the dimensions of the resistor such as length or width. The resistivity value of a material is used to calculate the resistance of a resistor using the formula R = ρL/A, where ρ is the resistivity, L is the length of the resistor, and A is the cross-sectional area.

6. What is the best definition of Resistance?

V/I

The ability to stop a flow of current

The impedence of the flow of current

The PD divided by current through a component

Resistance is defined as the ratio of potential difference (PD) to the current flowing through a component. It quantifies the opposition offered by a material or device to the flow of electric current. The greater the resistance, the more difficult it is for current to flow. Therefore, the answer "the PD divided by current through a component" accurately describes the best definition of resistance.

Explanation

Resistance is defined as the ratio of potential difference (PD) to the current flowing through a component. It quantifies the opposition offered by a material or device to the flow of electric current. The greater the resistance, the more difficult it is for current to flow. Therefore, the answer "the PD divided by current through a component" accurately describes the best definition of resistance.

7. What is Ohm's Law?

V=IR, where V=Potential difference, I=current, R=resistance

R=V/I where V=Potential difference, I=current, R=resistance

Current is proportional to Potential difference

A resistor will have a constant resistance at a fixed temperature whatever the current.

A resistor has a constant resistance.

A resistor will have a constant resistance at a fixed temperature whatever the current. This statement explains Ohm's Law, which states that the current passing through a conductor is directly proportional to the potential difference across it, and inversely proportional to its resistance. In other words, the resistance of a resistor remains constant regardless of the current flowing through it, as long as the temperature remains constant.

Explanation

A resistor will have a constant resistance at a fixed temperature whatever the current. This statement explains Ohm's Law, which states that the current passing through a conductor is directly proportional to the potential difference across it, and inversely proportional to its resistance. In other words, the resistance of a resistor remains constant regardless of the current flowing through it, as long as the temperature remains constant.