Ch 19 - (Electrical Circuits) Flashcards
What are power supplies?
cells, batteries, power supplies and generators all supply current to the circuit
What are resistors?
potential dividers, fixed and variable resistors, thermistors and light dependent resistors (LDR’s) control current
What are meters?
ammeters and voltmeters are used to measure the current and potential difference
- Ammeters in series
- Voltmeters in parallel
What are electromagnetic components?
Magnetizing coils, relays, and transformers use electromagnetic effects
- relay use small current in one circuit to switch on another
- transformers ‘step up’ and ‘step down’ current and potential difference.
What are fuses?
Protect expensive components from current surges and act as safety measures against fire
What are thermistors?
- non - ohmic conductor
- temperature dependent resistor
- resistance changes based on temp
- as temp increases, resistance of thermistor decreases
What are light - dependent resistors?
- non-ohmic conductor
- sensory resistor
- resistance changes depending on light intensity (illumination)
- as light intensity increases, resistance of LDR decreases
What is a diode?
allows a current in one direction
What happens if diode is placed in a.c. ?
Only allows a current half of the time (called as rectification)
How is the current in a series circuit? And why?
- same value at any point
- no. of electrons passing through per sec is same ate very part
What does the current flowing around series circuit depend on?
- Voltage of power source
- resistance of components in a circuit
What does increasing voltage do in a series circuit?
drives more current around the circuit
What does increasing number of components do in a series circuit?
increases the total resistance
What is the advantage in a parallel circuit?
- The components can be individually controlled, using their own switches
- If one component stops working the others will continue to function
How does Curr not flow in a parallel circuit?
- In a parallel circuit, the current splits up
- current in each branch will be smaller than the current from the power supply
What happens at every junction in parallel circuit and why?
-The current is conserved
- amount of current flowing into the junction is equal to the amount of current flowing out of it
Why does current split up in junctions?
charge is conserved
What happens when current does not split up equally at junctions in a series circuit?
The current in each branch will only be identical if the resistance of the components along each branch are identical
why does current behave a certain way in a series circuit?
- Electrons are physical matter – they cannot be created or destroyed
- total number of electrons (and hence current) going around a circuit must remain the same
- When the electrons reach a junction, however, some of them will go one way and the rest will go the other
How do you find the potential difference in series circuit?
several cells are connected together in series, their combined EMF is equal to the sum of their individual EMFs
How do you find potential difference in parallel circuits?
- potential difference across each component connected in parallel is the same
This is the opposite of the current, which is different in each branch
what are the advantages of parallel circuits?
- The components can be individually controlled, using their own switches
- If one component stops working the others will continue to function