To determine the effect of multiple resistors on current in a circuit
Apparatus:
Battery
Resistors
Light bulb
Wires
Method:
Construct the following circuits
Rank the three circuits in terms of the brightness of the bulb.
Conclusions:
The brightness of the bulb is an indicator of how much current is flowing. If the bulb gets brighter because of a change then more current is flowing. If the bulb gets dimmer less current is flowing.
You will find that the more resistors you have the brighter the bulb.
Why is this the case? Why do more resistors make it easier for charge to flow in the circuit? It is because they are in parallel so there are more paths for charge to take to move. You can think of it like a highway with more lanes, or the tube of marbles splitting into multiple parallel tubes. The more branches there are, the easier it is for charge to flow. You will learn more about the total resistance of parallel resistors later but always remember that more resistors in parallel mean more pathways. In series the pathways come one after the other so it does not make it easier for charge to flow.
Two
$8\phantom{\rule{2pt}{0ex}}\mathrm{k}\Omega $ resistors are connected in parallel. Calculate the equivalent resistance.
The equivalent resistance of two
$8\phantom{\rule{2pt}{0ex}}\mathrm{k}\Omega $ resistors connected in parallel is
$4\phantom{\rule{2pt}{0ex}}\mathrm{k}\Omega $ .
Two resistors are connected in parallel. The equivalent resistance is
$100\phantom{\rule{2pt}{0ex}}\Omega $ . If one resistor is
$150\phantom{\rule{2pt}{0ex}}\Omega $ , calculate the value of the second resistor.
The second resistor has a resistance of
$300\phantom{\rule{2pt}{0ex}}\Omega $ .
Resistance
What is the unit of resistance called and what is its symbol?
Explain what happens to the total resistance of a circuit when resistors are added in series?
Explain what happens to the total resistance of a circuit when resistors are added in parallel?
Why do batteries go flat?
The following presentation summarizes the concepts covered in this chapter.
Exercises - electric circuits
Write definitions for each of the following:
resistor
coulomb
voltmeter
Draw a circuit diagram which consists of the following components:
2 batteries in parallel
an open switch
2 resistors in parallel
an ammeter measuring total current
a voltmeter measuring potential difference across one of the parallel resistors
Complete the table below:
Quantity
Symbol
Unit of meaurement
Symbol of unit
e.g. Distance
e.g. d
e.g. kilometer
e.g. km
Resistance
Current
Potential difference
Draw a diagram of a circuit which contains a battery connected to a lightbulb and a resistor all in series.
Also include in the diagram where you would place an ammeter if you wanted to measure the current through the lightbulb.
Draw where and how you would place a voltmeter in the circuit to measure the potential difference across the resistor.
Thandi wants to measure the current through the resistor in the circuit shown below and sets up the circuit as shown below. What is wrong with her circuit setup?
[SC 2003/11] The emf of a battery can best be explained as the
$\cdots $
rate of energy delivered per unit current
rate at which charge is delivered
rate at which energy is delivered
charge per unit of energy delivered by the battery
[IEB 2002/11 HG1] Which of the following is the correct definition of the emf of a battery?
It is the product of current and the external resistance of the circuit.
It is a measure of the cell's ability to conduct an electric current.
It is equal to the “lost volts” in the internal resistance of the circuit.
It is the power supplied by the battery per unit current passing through the battery.
[IEB 2005/11 HG] Three identical light bulbs A, B and C are connected in an electric circuit as shown in the diagram below.
How bright is bulb A compared to B and C?
How bright are the bulbs after switch S has been opened?
How do the currents in bulbs A and B change when switch S is opened?
Current in A
Current in B
(a)
decreases
increases
(b)
decreases
decreases
(c)
increases
increases
(d)
increases
decreases
[IEB 2004/11 HG1] When a current
$I$ is maintained in a conductor for a time of
$t$ , how many electrons with charge e pass any cross-section of the conductor per second?
It
It/e
Ite
e/It
Questions & Answers
use the y -intercept and slope to sketch the graph of the equation y=6x
An investment account was opened with an initial deposit of $9,600 and earns 7.4% interest, compounded continuously. How much will the account be worth after 15 years?
Absolutely, for me. My problems with math started in First grade...involving a nun Sister Anastasia, bad vision, talking & getting expelled from Catholic school. When it comes to math I just can't focus and all I can hear is our family silverware banging and clanging on the pink Formica table.
Carole
I'm 13 and I understand it great
AJ
I am 1 year old but I can do it! 1+1=2 proof very hard for me though.
Atone
Not really they are just easy concepts which can be understood if you have great basics. I am 14 I understood them easily.
Vedant
hi vedant can u help me with some assignments
Solomon
find the 15th term of the geometric sequince whose first is 18 and last term of 387
If f(x) = x-2
then, f(3) when 5f(x+1)
5((3-2)+1)
5(1+1)
5(2)
10
Augustine
A soccer field is a rectangle 130 meters wide and 110 meters long. The coach asks players to run from one corner to the other corner diagonally across. What is that distance, to the nearest tenths place.
Jeannette has $5 and $10 bills in her wallet. The number of fives is three more than six times the number of tens. Let t represent the number of tens. Write an expression for the number of fives.
why surface tension is zero at critical temperature
Shanjida
I think if critical temperature denote high temperature then a liquid stats boils that time the water stats to evaporate so some moles of h2o to up and due to high temp the bonding break they have low density so it can be a reason
s.
Need to simplify the expresin. 3/7 (x+y)-1/7 (x-1)=
The fundamental frequency of a sonometer wire streached by a load of relative density 's'are n¹ and n² when the load is in air and completly immersed in water respectively then the lation n²/na is