Electricity and Energy Flashcards
Describe what is meant by electromagnetic radiation.
All EM radiation travels at the speed of light in a vacuum (3x10^8 ms-1).
Exhibits wave properties as it transfers energy through space. It has both electric and magnetic field components which oscillate in phase, perpendicular to each other and to the direction of energy propagation.
State what is meant is meant by Lenz’s Law.
Len’s law states that the direction of the current induced in a conductor by a changing magnetic field is such that the magnetic field created by the induced current opposes the initial changing magnetic field which produced it.
Explain what is special about iron, nickel and cobalt.
They exhibit a magnetic effect called ferromagnetism, in which magnetic dipoles can be mac to align, resulting in the material becoming magnetised.
Explain why electrons follow a curved path between parallel deflection plates.
The electrons travel with (constant) horizontal velocity.
Electrons travel with (constant) vertical acceleration.
Electric Field definition.
A region where a charge experiences a force.
Electric field strength definition.
The force per unit positive charge.
Magnetic field definition.
A region where a moving charge experience a force.
Electric potential 0° definition.
The work done per unit positive charge in bringing the charge from infinity to a point.
Time constant definition.
The length of time for voltage to reach 63% of total voltage whilst charging or 37% of total voltage whilst discharging.
Capacitive reactance definition.
Opposition of a capacitor to a changing current.
Back EMF definition.
An e.m.f. is induced in a coil when the current in the coil is changing. This induced e.m.f. opposes the change in current.
Electronvolt (eV)
Energy acquired when one electron accelerates through a potential difference of 1 volt.
Explain why a charged particle follows a helical path when moving in a magnetic field.
Component of velocity perpendicular to the field results in circular motion.
Component of the velocity parallel to the field is constant.
After how many time constants can a capacitor in an RC circuit be considered to be fully charged.
5T
Inductance definition.
When a moving or varying magnetic field cuts a conductor to create an electromotive force (e.m.f.) across it. OR When a conductor is moved perpendicular to a magnetic field it will generate an e.m.f. across the conductor.
