mark scheme stuff

Question 1

what happens to ammeter when extra resistors are connected in parallel circuit

Answer 1

MP1. resistance (of circuit) decreased;
MP2. (because) extra path in circuit;
MP3. resistance (of circuit) halved;
MP4. idea that voltage across parallel branches is
the same (as previous voltage);
MP5. current (in ammeter) increased;
MP6. current (in ammeter) doubled;

Question 2

why is there an alternating current in a ring that is detected underground from a metal detector

Answer 2

idea of changing magnetic field
idea of gold ring cutting field lines;
ignore ring interacting
with field
idea of induced voltage for gold ring;

Question 3

how does A.C in receiving coil cause sound to be emitted from loudspeaker

Answer 3

MP1. alternating current in loudspeaker;
MP2. magnetic fields interact (in loudspeaker)
MP3. causing a force (on loudspeaker cone);
MP4. a.c. causes changing force direction;
MP5. loudspeaker (cone) vibrates;