# Physics IB glossary - electricity and magnetism

## 18 terms

### Coulomb's law

F=k (Q₁Q₂/r²)
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.

### Current

charge per unit time passing through cross-sectional area.

### Electric field

electric force per unit charge experienced by positive test charge. Vector.
point charge Q produces electrical field magnitude
E=k (lQl/r²)

### electric potential

V=k(Q/r)
work per unit charge in bringing test charge from infinity to a given point within electric field. electric potential is constant within conductor. scalar.

### Electric Power

P=VI=RI²=V²/R
rate of dissipation of electrical energy

### Electron volt

1eV=1.6x10⁻¹⁹J
work done moving charge of e=1.6x10⁻¹⁹ through PD of 1volt.

### Emf

work done in moving a positive test particle across the terminals of a battery. εI = total power dissipated when I is current in circuit.

ε=N (ΔΦ/Δt)
induced emf in loop is rate of change with time of magnetic flux linkage through the loop.

### Lenz's law

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)

Φ=NBAcosθ scalar.
product of magnetic field strength, area of loop, no. turns of wire, and cosine of angle between the area normal and B

### Magnetic force

F=qvBsinθ = BILsinθ
moving charged particle or current will experience force in a magnetic field.

### Ohm's law

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.

R=V/I

### Rms current

√ of average of square of current.
for sinusoidally varying currents = peak voltage/ √2

### Rms voltage

√ of average of square of voltage.
for siusoidally varying voltage = peak voltage / √2