P6 - Electric circuits Flashcards
What are the two types of circuits
series and parallel
In a series circuit the current is all the
same at all points within the circuit
The current in a circuit can be measured with an
ammeter
Voltage across a component can be measured using a
voltmeter
In a parallel circuit the current
splits between the two branches of the circuit meaning that the current from the source is larger than the current in a branch
In a parallel circuit the current from the source is the sum of the
currents in the separate branches of the circuit
A1 = A2 + A3
In a series circuit with 2 resistors the combined resistance is
the sum of the 2 resistors
R1 + R2 = RC
In a parallel circuit the combined resistance is
less than the value of either of the two resistors because there are more paths for the charge to pass along
When resistors R1 and R2 are in a parallel circuit RC is
RC = (R1 X R2)/(R1 + R2)
In series circuit the p.d across the battery equals
the sum of the p.d across each lamp
A battery is made by joining
cells together
the total e.m.f of three cells would be
E = E1 + E2 + E3
The sum of the individual e.m.f of the cell
In series circuits resistors oppose
the flow of electric current through the circuit.
total e.m.f of all energy sources =
total p.d across components
What are the advantages of connecting a lamp to a parallel circuit over a series circuit
- Each lamp can be switched on and off separately in a parallel circuit but in a series circuit they all switch off
- If one lamp breaks current still flows through the other ones in a parallel circuit but in a series circuit if the lamp breaks the whole circuit stops.
An input transducer is a circuit that turns a variable outside of the circuit such as temperature or light
into an electrical signal
Thermistors and light dependent resistors (LDR)s can be used to make
input transducers.
A thermistor is a component whos resistance changes with its
temperature
Increasing temperature in a thermistor
decreases resistance
A light dependent resistor (LDR) resistance changes
with light intensity
Increasing light intensity in a LDR
decreases resistance
The change in resistance of an LDR or thermistor changes the
p.d across the resistor
A transducer is a device that transfers
energy from one form to another
What are some dangers of electricity
Damaged insulation: can get electric shock
Overheating of cables: can cause a fire
damp conditions: water conduct electricity
Fuses and circuit breakers protect us from electrical appliances by stopping the
flow of electric current flow if it gets too high stopping overheating
Circuit breakers help
switch off the flow of current if too high
Fuses contain thin wires that melt if
current is too high in appliance and breaks the circuit
What are fuse ratings
tells the level where a fuse will begin to melt
The fuse chosen should have a value
just above the normal current of an appliance
If an operating current is 3.9 A what is a suitable fuse value 3A 5A or 15A
5A since its just above the normal 3.9A
Explain why is a 13 A fuse wrong to use for an appliance with a 3.9 A operating current
More than three times the normal operating current is needed to melt the fuse.
Therefore, the 13 A fuse might not melt even if the appliance developed a fault.
