Energy and voltage in circuits

Question 1

Why are series or parallel circuits more appropriate for different applications?

Answer 1

for series the different components are connected in a line, end to end so if you remove one the whole circuit is broken and stop working. this is not handy so series is used for fairy lights etc.
for parallel each component is separate so if one thing is disconnected then the whole series will continue and so used in lighting (household electrics)

Question 2

How does the current in a series circuit depend on the applied voltage and nature of other components?

Answer 2

theres a bigger supply p.d when more cells are in series (if connected same way), the current is the same everywhere (I1=I2) and the size of the current depends on the total potential difference and the total resistance
the total p.d is shared between components and depends on resistance
total resistance depends on the no of components and type, total resistance is the sum of each component

Question 3

What is the equation linking energy transferred, charge, voltage?

Answer 3

E = QV

energy transferred= charge x voltage

Question 4

How does the current in a parallel circuit depend on the applied voltage and nature of other components?

Answer 4

p.d is same across all branches ( V1 = V2)
current shared between branches, total current is total of all currents through separate components (I total = I1 +I2)
junctions where current splits to rejoins, the total current going into = leaving because charge cannot disappear
current depends on resistance, higher resistance, harder for charge to flow, so low current (identical components have same current), total resistance decreases if a 2nd resistor is added

Question 5

What is voltage? (and symbol)

Answer 5

energy transferred per unit charge passed
joule per coulomb
if you increase voltage, more current, increase resistance, less current

Question 6

How can LEDs and lamps be used in circuits?

Answer 6

indicate the presence of current in a circuit because they it light when current flows through them in forward direction and cannot burn out

Question 7

What is the equation linking voltage, current and resistance?

Answer 7

voltage = current x resistance
V = IR

Question 8

How does an LDR change resistance?

Answer 8

type of resistor that changes resistance based on light falling on it, in bright light the resistance falls and in darkness it is highest, useful for burglar detectors

Question 9

How does an thermistor change resistance?

Answer 9

temp dependant resistor, in heat the resistance drops and in cool it goes up, useful temp detectors (thermostats)

Question 10

What is a.c and d.c?

Answer 10

alternating current, always changes direction

direct current, always same direction (cells and batteries)

Question 11

How would you investigate how current varies with voltage for different components?

Answer 11

1. set up circuit w switch, variable resistor, voltmeter (w wire) and ammeter
2. turn variable resistor to max value
3. take readings from a/v
4. alter value of vr and take new readings
5. repeat 6 times

Question 12

How does current change with voltage in wires, resistors, metal filament lamps and diodes?

Answer 12

wire/resistor - graph has straight line, resistance does not change
filament - not straight (curve-ish), resistance changes,higher current/voltage resistance increases and temp increases, current increases
diode - on x axis and then straight line up, high resistance when current is in one direction but low when opposite

Question 13

Why is current conserved at a junction?

Answer 13

because the no of electrons that flow into a junction each second must equal the no that leave each second