DC circuits and their laws Flashcards
What is kirchoff’s first law?
At any junction in a circuit, the total current leaving the junction is equal to the total current entering the junction.
Is the current passing through two or more components in series the same through each component, or different?
The same
When does p.d drop?
When charge carriers lose energy, by passing through a component.
When does p.d rise?
When charge carriers gain energy, by passing through a a battery or a cell’s terminal.
What is the rule for p.d in a series circuit?
The p.d across components in series is equal to the total p.d across each component
What is kirchoff’s second law?
For any complete loop of a circuit, the sum of the E.M.F’S around the loop is equal to the sum of the potential drops around the loop.
What are the two power equations derivated from P=IV?
P = I(squared) R and P = V(squared) / R
What causes an internal resistance?
Internal resistance is due to opposition of the flow of charge through the source.
What is the definition of E.M.F?
The electrical energy per unit charge produced by the source.
Why is the terminal p.d less than the EMF whenever current passes through the source?
This is due to internal resistance, which is the loss of potential difference per unit current when current passes through the source.
What is the formula for e.m.f?
IR + Ir.
What is the lost p.d inside a cell equal to?
The difference between the e.m.f of the cell and the p.d across its terminals. V=ℰ-Ir
What happens therefore when a current flows through a source which has internal resistance?
This leads to “lost volts” inside the cell. So the p.d across the terminals decreases.
What is a potential dividor?
Two or more resistors connected in series with each other across a source of fixed p.d
What is rule for potential dividor?
The ratio of pd across each resistor is equal to the ratio of resistance across each resistor.
