Beatty 6091_WS_Electromagnetism_teacher (Updated 2021

1 A. Prior Knowledge Before T / F Statement After T / F 1. All metals (Al, Cu, Fe) can be magnetized. F 2. Iron is attracted to magnet, so attraction is a sure test of magnetism. F 3. The strength of the electromagnet can be increased by changing the direction of the current. F 4. A force is acting on a current-carrying wire if it is in a magnetic field. T 5. A circuit breaker should be made by a permanent magnet. F 6. A circuit breaker and an electric bell make use of magnet in their operations. T Beatty Secondary School Secondary 4E Pure Physics Electromagnetism Name: __________________________ ( ) Class: __________ Date: _____________ Learning Outcomes (a) draw the pattern of the magnetic field due to currents in straight wires and in solenoids and state the effect on the magnetic field of changing the magnitude and/or direction of the current (b) describe the application of the magnetic effect of a current in a circuit breaker (c) describe experiments to show the force on a current -carrying conductor, and on a beam of charged particles, in a magnetic field, including the effect of reversing (i) the current (ii) the direction of the field (d) deduce the relative directions of force, field and current when any two of these quantities are at right angles to each other using Fleming’s left-hand rule (e) describe the field patterns between current s in parallel conductors and relate these to the forces which exist between the conductors (excluding the Earth’s field) (f) explain how a current -carrying coil in a magnetic field experiences a turning effect and that the effect is increased by increasing (i) the number of turns on the coil (ii) the current (g) discuss how this turning effect is used in the action of an electric motor (h) describe the action of a split -ring commutator in a two -pole, single-coil motor and the effect of winding the coil on to a soft-iron cylinder

2 A) Magnetic effect of current When current flows through a wire, a magnetic field is produced around it. B) Magnetic field of current-carrying conductors • The magnetic field of a straight , current -carrying wire consists of concentric circles. • The magnetic field is stronger closer to the wire. Method to identify direction of magnetic field in a wire: Right hand grip rule • The right-hand grip rule can be used to determin e the direction of the magnetic field created by a straight wire carrying a current. • The thumb points in the direction of the current. • The other fingers point in the direction of the magnetic field around the wire. When no current flows through XY, the compass needles point to the north. When current flows through XY, the needle of compass A points to the east. The needle of compass B points to