units 18-21 Flashcards
(21 cards)
What is an electric field?
The force per unit positive charge.
What does the direction of an electric field line indicate?
It indicates the direction in which a positively charged atom would flow.
What is a test charge?
A small positive charge that feels the force of the electric field without distorting it.
Where is charge stored on a sphere?
Charge is stored on the surface of a sphere; the electric field is zero within the sphere.
Describe the electric field strength between parallel plates
It is equal, with field lines in a uniform electric field being parallel and equally spaced.
What does Coulomb’s law state?
Any two point charges exert an electrical force on each other that is proportional to the product of their charges and inversely proportional to the square of the distance between them.
How does electric field strength differ between point charges and a single point charge?
Electric field strength between two point charges is different from that due to a single point charge.
What is electrical potential at a point?
It is the work done per unit positive charge in bringing a small positive test charge from infinity to that point.
What is a magnetic field?
A field of force produced by either moving charges or by permanent magnets.
What does the direction of a magnetic field show?
The direction of the magnetic force of an isolated north pole.
What is magnetic flux density?
The force acting per unit current per unit length of wire placed at right angles to the magnetic field.
What is magnetic flux?
The product of the magnetic flux density and the cross-sectional area perpendicular to the direction of the magnetic flux density.
What is magnetic flux linkage for a coil with a number of turns?
The product of the magnetic flux and the number of turns.
What is Faraday’s Law?
The magnitude of the induced emf is proportional to the rate of change of magnetic flux (linkage).
What is Lenz’s Law?
Any induced current or emf will be established in a direction so as to produce effects that oppose the change that is producing it.
What is capacitance?
The capacitance of a parallel plate capacitor is equal to the charge stored on one plate per unit potential difference between the plates.
What is the capacitance of an isolated body?
It is the charge stored per unit potential difference.
How do you calculate total capacitance for capacitors in parallel?
CT = C1 + C2
Voltage is the same for all capacitors.
How do you calculate total capacitance for capacitors in series?
Voltage is individual for all capacitors, charge is equal for all.
Qt = Q1 = Q2
What is the mean power transferred in a circuit with sinusoidal alternating current?
It is half of the maximum power.
What is rectification?
The conversion from an alternating current to a direct current.
