P6 MIDTERMS

concepts and terminologies

electric current (I)

The rate of the flow of charge Q through a cross-section A in a unit of time t.

ampere (A)

the charge flowing at the rate of coulomb per second

electron flow

the direction of e- flowing from – to +

conventional current

the motion of +q from + to – has same effect

source of electromotive force (emf)

a device that uses chemical, mechanical or other energy to provide the potential difference necessary for electric current

electrical circuits

often contain one or more resistors grouped together and attached to an energy source, such as a battery

Ohm’s law

states that the current (I) through a given conductor is directly proportional to the potential difference V between its end points

length (L)

area (A)

temperature (T)

material

factors affecting resistance

longer

in terms of length, _______ materials have greater resistance

larger

in terms of area, _______ areas offer LESS resistance

higher

in terms of temperature, _______ temperatures usually result in higher resistances

iron

in terms of material, _____ has more electrical resistance than a geometrically similar copper conductor

resistivity

a property of a material that determines its electrical resistance (R)

temperature coefficient of resistance

the change in resistance per unit resistance per unit degree change of temperature

series

resistors are said to be connected in _______
when there is a single path for the current

complex

a _______ circuit is one containing more than a single loop and different current paths

parallel

resistors are said to be connected in ________
when there is more than one path for current