4.3 ELECTRICAL CIRCUITS Flashcards
what is Kirchoff’s Second Law?
Kirchoff’s Second Law states that in any closed loop. the sum of the e.m.f is equal to the sum of the products of the current and the resistance
(in other words the total potential difference is equal to the sum of all the potential differences of the components)
∑Ɛ = ∑IR
what is Kirchoff’s First law?
Kirchoff’s First law states the sum of currents entering a junction in a circuit is equal to the sum of the currents leaving the junction
what is Kirchoff’s Second Law a consequence of?
the conservation of energy
what is Kirchoff’s First Law a consequence of?
the conservation of charge
what is the equation for total resistance in a series circuit?
Rtotal = R1 + R2 + R3
(opposite to spring constant and capacitors)
what is the equation for total resistance in a parallel circuit?
1 / Rtotal = 1 / R1 + 1 / R2 + 1 / R3 opposite to capacitors and spring constants
how are ammeters connected in circuits and what is the resistance of them?
connected in series, designed to be close to zero resistance
how are voltmeters connected in circuits and what is the resistance of them?
connected in parallel, designed to have close to infinite resistance so that none of the current flows through them
what is the rule for current in series circuits?
stays the same
what is the rule for current in parallel circuits?
splits at junctions
what is the rule for voltage in series circuits?
splits, the voltage of the cell is equal to the sum of the voltages across the components (not necessarily and equal split)
what is the rule for voltage in parallel circuits?
the same, each branch has the same voltage as the cell (so would split if there were more than one component on the same branch)
what is internal resistance?
internal resistance of a source of e.m.f is the resistance to electric current of the materials inside, when current flows energy is transferred to these materials resulting in the p.d dropping
what is the difference between the e.m.f and the terminal p.d known as?
the ‘lost volts’
define terminal p.d
the potential difference recorded across the terminals of the cell