electromagnetism Flashcards
what are 3 ways the strength of an electromagnet can be increased
increase current
increase number of turns in coil
insert a soft iron rod into the coil
suggest one situation where turning the magnet on and off would be an advantage
at a car dump
what does d.c. and a.c. mean
direct current and alternating current
how does current forces cause the loop to rotate
where the current goes in it pushes up and where it goes out it pushes down causing it to rotate
why is there no current in the coil when it is vertical
At the instant the plane of the coil is vertical, the magnetic flux linked with the coil
is at a maximum, but it is not changing.
A changing flux is required to induce an e.m.f.
why does the coil work best when it is horizontal
At the instant the plane of the coil is horizontal, the magnetic flux linked with
the coil is zero, but it is changing at its maximum rate.
A flux changing at maximum rate induces a maximum e.m.f.
what are 3 ways the current could be increased in the coil
At the instant the plane of the coil is horizontal, the magnetic flux linked with
the coil is zero, but it is changing at its maximum rate.
A flux changing at maximum rate induces a maximum e.m.f.
what would the current be on an ammeter when the switch is closed
When the switch is closed there is a momentary deflection on the needle to the right on the ammeter before it returns once more to zero.
what would the current be on an ammeter when the switch is open
When the switch is closed there is a momentary deflection on the needle to the left on the ammeter before it returns once more to zero.
how is a.c. different to d.c.
In a d.c. circuit, the current flows in the same direction all the time. An a.c. current reverses its direction regularly.
what core is used in most transformers
a soft iron core
