electric force between two point charges.
also for two spherical objects, where r is measured from centre to centre. attractive for unlike charges and repulsive for like charges.
charge per unit time passing through cross-sectional area.
electric force per unit charge experienced by positive test charge. Vector.
point charge Q produces electrical field magnitude
work per unit charge in bringing test charge from infinity to a given point within electric field. electric potential is constant within conductor. scalar.
rate of dissipation of electrical energy
work done moving charge of e=1.6x10⁻¹⁹ through PD of 1volt.
work done in moving a positive test particle across the terminals of a battery. εI = total power dissipated when I is current in circuit.
induced emf in loop is rate of change with time of magnetic flux linkage through the loop.
direction of induced current is such to oppose change that created it.
Magnetic field strength
vector. magnitude is given by force on a unit charge moving at right angles to field with unit velocity. MFS, B, is at right angles for force it exerts. measured in Tesla.
in straight wire: B=μ₀ (I/2πr)
in solenoid : B=μ₀ (NI/L)
Magnetic flux linkage
product of magnetic field strength, area of loop, no. turns of wire, and cosine of angle between the area normal and B
F=qvBsinθ = BILsinθ
moving charged particle or current will experience force in a magnetic field.
current in a conductor at constant T is proportional to voltage across it.
path in electric field
for charged particle: parabola, or straight line if particle moves along a straight field line.
path in magnetic field
for charged particle: circle if moving at right angle to field, a helix, or a straight line if particle moves along a straight field line.
radius of circular path: R=mv/qB
√ of average of square of current.
for sinusoidally varying currents = peak voltage/ √2
√ of average of square of voltage.
for siusoidally varying voltage = peak voltage / √2