deck_5450802 Flashcards
In a parallel circuit the element with the least resistance …
consumes the most power
what will happen if an ammeter is connected in series with a resistor?
Almost all the current will flow through the ammeter
What will happen when a voltmeter is connected in series with a resistor?
It will show a 0 volts reading.
Kirchofff’s voltage law can be stated as
The sum of the voltage drops around any closed path is 0
What can kirchoff’s current law be stated as?
The sum of the current entering a node is equal to the sum of current leaving the node.
If a 40w and 60w light bulb are connected in series to the mains, which will glow brighter?
The 40w.It has the higher resistance.
If there was a circuit with 3 bulbs in series and one of them was removed, what would happen to the total power dissipated?
It would increase. Circuit resistance has fallen.
If there was a circuit with 3 bulbs in parallel and one of them was removed, what would happen to the total power dissipated?
Circuit resistance has increased and the power would fall.
If a 9v power source was in a series circuit with an LED (turn on voltage=2.2v) and a resistor of resistance 680 ohms, what would be the expression for current in the circuit?
(9-2.2) / 680
What is a perfect voltage source?
The current going through it will change to ensure the pd is always constant.
What is conductance?
The inverse of resistanceI=V*G. Units=siemens
What do we assume the p.d across a LED to be?
The turn on voltage. We assume the I/V graph of an LED to be vertical at the turn on voltage.
If you had a circuit with a R1 and R2, how would you maximise the power in R2?
Make R1 and R2 equal to each other.The efficiency will be 50%
If you had a circuit with R1 and R2, how would you maximise the efficiency of power to R2?
Make R2 large and R1 small.
True or false. Two waves are out of phase when they have different phases or one is ahead or behind the other.
False. They are out of phase when one is ahead or behind the other.
When a capacitor and resistor are in parallel, what will the p.d across them be in relation to each other?
They will be the same.
How do you find the reactance of a capacitor?
= 1/ (2pif*C)
In a capacitive circuit, what is the relationship between input and output voltage?
Output lags input
In a capacitive voltage divider, what happens to output voltage with an increase in frequency?
It falls.
In a capacitive circuit, what are the output and input frequencies?
The same.
If the capacitance of a capacitor is increased, what happens to the current drawn?
It increases.
What is the definition of capacitance?
charge = capacitance*voltage
If an LED has a turn on voltage of 1.8v, what will the P.D across it be?
1.8v
When are two components in parallel?
When they share two terminals.