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What factors would affect the resistance of lightbulbs - Coggle Diagram
What
factors
would affect the
resistance
of lightbulbs
PHYSICS
concepts
Ohms Law
V = IR
V(voltage), I(current), R(resistance)
Kirchhoff's Laws
1.The total current going into a junction, must be equal to the total current leaving the junction - I1 = I2 + I3
The sum of all the potential differences across the loads is equal to the potential difference supplying the load - Vt = V1 + V2 + V3
R = ρL/A
R(resistance), ρ(resistivity), L(length), A(cross-sectional area)
WIRES
type of wire (
material)
copper, aluminium, steel, tin, and silver
will use these materials/light bulbs as they exhibit a range of resistance (qualities) as a group, which is useful to compare them and how the type affects the resistance
different materials exhibit different resistance - for e.g. silver and copper have low resistance, while steel has a higher resistance
TEST
- set up circuit with copper wires having constant thickness and lengths. measure voltage (voltmeter) and current (ammeter) to calculate resistance with Ohms Law. repeat x 3 for copper wire, then repeat these steps for the other materials of wire
length
of wire
10cm, 20cm, 30cm, 40cm, 50cm
these lengths offer a range of lengths, so the change in resistance would be easy to compare
R ∝ L
a longer wire will increase the resistance as they would be more atoms for the electrons to collide with
thickness
of wire
thicker wires will have lower resistance than thinner wires, as thicker wires offer more space for electrons to flow reducing the number of collisions
TEST
- **set up a circuit with wires of the same length and thickness, but having 0.5mm thickness. measure voltage and current with voltmeter and ammeter. calculate resistance with Ohms Law. repeat x 3 for this thickness, then do these steps for the other thicknesses.
relates to cross-sectional area; directly proportional to it
thicker wire - larger cross sectional area
R ∝ 1/A
0.5mm, 1mm, 2mm
LIGHT BULB
type
of light bulb
LED, CFL, incandescent, halogen, fluorescent
different types of light bulbs have different resistance characteristics, due to their materials. for e.g. generally incandescent lights have more resistance, while LEDS are said to have the least resistance
TEST
- set up in a circuit with the specific lightbulb, then measure the voltage and current using a voltmeter and ammeter. then calculate the resistance using Ohms Law. repeat three times for each lightbulb **
EQUIPMENT
needed to measure
power supply/battery
wires
lightbulbs
alligator clips
ammeter (current)
voltmeter (voltage/potential difference)
CIRCUIT CONFIGURATION
Series
as the total resistance is the total sum of the individual resistances, adding more resistors would increase the total resistance
resulting in current decreasing, as voltage remains constant
Parallel
total resistance decreases, less than the resistance of any individual resistor in a parallel branch
current increases as resistance decreases
TEST
- set up a series circuit with 2 or more lightbulbs and a parallel circuit with the same number of lightbulbs. keep the voltage, type of lightbulbs, a wire material/length/thickness constant. use voltmeter and ammeter to calculate resistance with Ohms Law**
RISKS
electric shock
- precautions: insulated wires, turn off power before adjusting
burns from overheating
- wait for the component/s to cool down before touching, use components that are rated for the power suppling
broken glass
from lightbulb - handle lightbulbs carefully, dispose them safely if broken, and use safety gear and closed in shoes
TRIALS
repeat
each variation of the independent variable
three times
this ensures reliable and consistent results, as the impact of random errors would be reduced, and more trials allow for more comparison and analysis of the results
TEMPERATURE
when temperature increases the number of atoms of the metal vibrate more, which increases the number of collisions between the electrons and atoms, which increases resistance
FEASIBILITY
all the variables are
feasible
under school lab conditions, as the school would already have the required equipment to use.**
however, different types of lightbulbs and/or wires available in the school may be limited or hard to access.
WHAT
is it
An electric circuit is a closed, complete pathway that electric current flows through.
