Chatper 27 - Direct-current Circuits

what is emf?

it is the max possible voltage the battery can provide brween its terminals

what is direct current?

the current in the ciruit is constant in magnitude and direction because the potential difference at the battery terminals is constant

what is internal resistance?

since a real battery is made up of matter, it has resistance to the flow of charge within the battery 

what is terminal voltage (delta V?

delta V = E - Ir 

e = emf 

I = current 

r= internal resistance 

Emf increases as we pass through battery, however the potential decreases by Ir when moving through resistance 

what is open circuit voltage?

the terminal voltage when current is zero

what is the load resistance?

what is a junction?

this is where the current can split in a circuit

What is Krichoff’s Rules? Think loops

1. Junction rule. At any junction, the sum of the currnets must equal zero

2. Loop rule. the sum of the potential differences across all elements around any closed circuit loop must be zero.

what is load resistance?

when the terminal voltage must equal the potential difference arcoss the external resistance R 

Emf = IR + Ir

what happens if a resistor is transversed in the direction of the current?

charges move from high-potenital ened of a rsitor to low potential end, so the potential differnce across the resistor is -IR

what happesn if you transverse a resistor oppostie to current?

the potential difference is +IR

what happens if you transve the source of emf in the direction of emf?

the potential difference is + E

what happens if you transerve the source in the oppostie direction of th eemft (pos to negative) ?

the potential difference is -E

what is an RC circuit?

An RC circuit is a circuit containing a seies combination of a resistor and a capacitor

what is charge as a function of time that for a capcitor being charged?

q(t) = CE(1-e^-t/RC) = Qmaz(1-e^-t/RC)

what is the current as a function of time for a cpacitor being charged

i(t) = E/R e^-t/RC

what is the time constant (t)

t = RC

• represents the time interval during which the current decreases to 1/e of the initial value

how do you find the energy required by the battery during a time interval to fully cahrge the capacitor?

Qmax*Emf= CEmf²

wha tis the enrgy stored in a capcitor after being fully charged?

1/2QmaxEmf = 1/2CEmf²

what is the charge as a function of time for a discharging capacitor?

q(t) = Qie^-t/RC

what is current as a function of time for a discharging capacitor?

i(t) = -Q/RCe^-t/RC