IB MYP Integrated Sciences e-Assessment : Generation and transmission of electricity Exam Style Practice Questions - New Syllabus
Question (9 marks)
When a current flows through a wire it generates a magnetic field. If the wire is coiled around a core, an electromagnet can be formed.
Question a (3 marks)
Select shapes to construct a diagram showing the magnetic field lines around and through the coil of wire below.
▶️Answer/Explanation
Answer: Diagram showing magnetic field lines around and through the coil of wire.
Detailed Solution: The magnetic field lines around a current-carrying coil form concentric circles. Inside the coil, the field lines are parallel and uniform, indicating a strong magnetic field.
Question b (3 marks)
The flow of the direct current through the coil generates a force. Select what happens to the coil when a direct current flows and explain why the generated force has this effect on the coil.
▶️Answer/Explanation
Answer: The force that is created due to the direction of the magnetic field and the direction of the flow of current will push downwards at the bottom of the coil and push up at the top of the coil. This will lead to the coil being pushed away from each other, thus expanding.
Detailed Solution: According to the right-hand rule, the magnetic field generated by the current interacts with the external magnetic field, creating a force that causes the coil to expand or contract depending on the direction of the current.
Question c (3 marks)
Music is one of the most common ways people express their ideas and feelings. The enjoyment of the beauty of music relies on electrical speakers which convert electrical signals into sound waves. The generation of the sound wave depends on the back and forth vibrational movement of the cone. Explain how this motion could be obtained by allowing an alternating current to pass in the coil.
▶️Answer/Explanation
Answer: As an alternating current is passed through the circuit, the coil attached to the cone will become an electromagnet that attracts to the permanent magnet when the power is supplied. Like this, the cone is stretched inwards. However, as the current is alternating, when it switches direction, the coil will create a magnetic field the other way, which will cause the electromagnet to repel and therefore push out. Like this, the motion of the cone can be controlled, and sound can be created.
Detailed Solution: Alternating current changes direction periodically, causing the magnetic field of the coil to reverse. This alternating attraction and repulsion between the coil and the permanent magnet create the back-and-forth motion of the cone, which generates sound waves.