Y11 SET 4

A company is designing a device that requires a magnet which can be easily turned on and off for lifting heavy metal objects in a scrapyard. Based on your understanding of magnetic materials and their properties, which type of magnet should they use, and why?

• Permanent magnet, because it always retains its magnetism.

• Electromagnet, because its magnetism can be controlled by switching the electric current on or off.

• Soft ferromagnetic magnet, because it is always magnetic.

• Non-magnetic material, because it is safer.

You are given a diagram showing magnetic field lines around a bar magnet. How would you use this diagram to determine the relative strength of the magnetic field at different points, and what evidence would you use to support your reasoning?

• The strength is greatest where the field lines are closest together, indicating a stronger magnetic field at the poles.

• The strength is greatest where the field lines are farthest apart, indicating a stronger field at the center.

• The strength is the same everywhere around the magnet.

• The strength is unrelated to the spacing of the field lines.

A student is given two rods, one made of plastic and one made of metal. After rubbing both rods with a cloth, the student observes that the plastic rod attracts small pieces of paper, while the metal rod does not. Using your understanding of electrostatic charges and conductors/insulators, explain why this occurs and what this experiment demonstrates about the properties of conductors and insulators.

• The plastic rod is an insulator and retains charge, while the metal rod is a conductor and loses charge quickly.

• Both rods are insulators, but only plastic can attract paper.

• The metal rod is an insulator and retains charge, while the plastic rod is a conductor and loses charge quickly.

• Both rods are conductors, but only metal can attract paper.

• 5 A, because current is charge divided by time (10/2).

• 20 A, because current is time divided by charge (2/10).

• 0.2 A, because current is charge multiplied by time (10*2).

• 12 A, because current is charge plus time (10+2).

If you double the length and halve the cross-sectional area of a metallic wire, how would its resistance change?

• The resistance would increase by a factor of four.

• The resistance would decrease by a factor of two.

• The resistance would remain the same.

• The resistance would decrease by a factor of four.

To calculate the cost of running an electrical appliance, which of the following steps should you follow?

• Find the power in kilowatts, multiply by the time in hours to get kWh, then multiply by the cost per kWh.

• Find the voltage and current, multiply them, and then divide by the time in hours.

• Find the resistance and current, multiply them, and then multiply by the cost per kWh.

• Find the power in watts, multiply by the time in seconds, then divide by the cost per kWh.

Which of the following best describes how you would sketch and interpret the current–voltage (I–V) graphs for a resistor of constant resistance, a filament lamp, and a diode, considering their different behaviors?

• The resistor shows a straight line, the filament lamp shows a curve that flattens, and the diode shows current only after a threshold voltage.

• All three show straight lines through the origin.

• The resistor and filament lamp both show curves, while the diode shows a straight line.

• The diode and filament lamp both show straight lines, while the resistor shows a curve.

Ohm’s Law states that the potential difference across a conductor is directly proportional to the current, provided certain conditions are met. Using strategic reasoning, what must remain constant for Ohm’s Law to apply, and why is this important?

• The temperature and physical properties of the conductor must remain constant to ensure the relationship between voltage and current is linear.

• The resistance must change with temperature for Ohm’s Law to apply.

• The current must remain zero for Ohm’s Law to be valid.

• The voltage must be kept at a maximum value for Ohm’s Law to work.

Given a circuit with a fixed voltage supply, how would increasing the resistance of the circuit affect the current, and what reasoning supports your answer based on Ohm’s Law?

• The current would increase because resistance and current are directly proportional.

• The current would decrease because resistance and current are inversely proportional.

• The current would remain the same because voltage is constant.

• The current would increase because voltage and resistance are inversely proportional.

A lamp is rated at 60 W and operates at a potential difference of 120 V. Using the power equation, determine the current flowing through the lamp and justify your calculation.

• 0.5 A, because current is power divided by voltage (60 W / 120 V).

• 2 A, because current is voltage divided by power (120 V / 60 W).

• 180 A, because current is power multiplied by voltage (60 W * 120 V).

• 60 A, because current is equal to the power rating (60 W).