Current of Electricity and DC circuits

taught by Math Arena

Course description

Overview

This course is targeted at Singapore Cambridge GCE O level students, but is also relevant to IGCSE students and Singapore's Integrated program students.

Circuits can seem really confusing the first time you see them. Wires are everywhere and the components are unrecognisable. The good news is that things become a lot easier once you gain a basic understanding of what each part in a circuit does and how it can be connected to other components. This course aims to do just that, allowing you to gain a greater understanding of what's going on in that messy bunch of connected components - you'll even learn to deal with factors such as internal resistance that you can't actually see!

Course Content

You will learn:

  • What exactly is current, voltage, charge, power, electromotive force, resistance and the other terms people like to use when talking about circuits
  • How the current, voltage, charge, power and other terms people like to use when talking about circuits all relate to each other
  • How increasing the number of resistors in a circuit can actually make its resistance go down
  • How increasing the amount of energy wasted in a circuit can actually make your battery last longer
  • Other weird, wacky, counterintuitive and cool stuff!

A link to the full O level Physics syllabus can be found here

Course Prerequisites

You will need to know:

  • How to watch videos on your computer
Math Arena
Math Arena

The instructor is from Math Arena.The instructor is absolutely passionate about teaching and you'll find the lessons engaging and ultimately rewarding.

Course Curriculum

Resistance - Resistivity and resistance
35:09
Q20 A wire which is 2 m long has a resistance of 16 Ω. What is the resistance of this wire if it is 1 m long?
Q21 Wire A has a resistance of 16 Ω. Wire B has the same dimensions as A but is made from a material which has half the resistivity of wire A. What is the resistance of wire B?
Q22 A 2 m long wire with a radius of 1 mm has a resistance of 16 Ω. What is the resistance of the same type of wire which is 4 m long and has a radius of 2 mm?
Q23 Wire A and Wire B have the following ratios. Length LA : Length LB = 5 : 18 Diameter DA : Diameter DB = 2 : 3 Resistivity ρA : Resistivity ρB = 4 : 9 What is the ratio of the resistance of wire A to the resistance of wire B?
Q24 Wire A and Wire B have the following ratios. Length LA : Length LB = 2 : 1 Diameter DA : Diameter DB = 2 : 3 Resistivity ρA : Resistivity ρB = 4 : 3. Given that the resistance of wire B is 2 Ω, what is the resistance of wire A?
Q25 A copper wire is part of a complete circuit through which current flows. Which graph best represents the relationship between the wire's length and its resistance?
Q26 A copper wire of length L and cross-sectional area X has resistance R. A second copper wire at the same temperature has a length of 2L and a cross-sectional area of 0.5 X. What is the resistance of the second copper wire?
Q27 The diagram below shows a circuit in which a copper wire connects points A and B. The electrical resistance between points A and B can be decreased by
Q28 The table shows the lengths and diameters of four copper wires. Which wire has the least resistance?
Q29 A student uses a length of wire as a resistor. He discovers that the resistance of the wire is too small. To be certain of making a resistor of higher value, he should use a piece of wire that is
Q30 The resistance of a metallic wire conductor is inversely proportional to its
Q31 In an experiment, four resistance wires made from the same material are connected in turn between the terminals P and Q in the circuit shown. The length and diameter of the wires are different. Which wire will give the smallest reading in the ammeter?
Effective Resistance - Basics
31:14
Q79 What is the effective resistance of the two resistors in the circuit shown below?
Q79 explanation
Q80 What is the effective resistance of the four resistors in the circuit shown below?
Q81 What is the effective resistance of the three resistors in the circuit shown below?
Q82 What is the potential difference across the 4 Ω resistor?
Q83 What is the potential difference across the 3 Ω resistor?
Q84 A power supply of 18V is connected to three resistors, as shown. What is the potential difference across the 2.0Ω resistor?
Q85 If the ammeter reading is 2 A and the voltmeter reading is 5 V, what is the e.m.f. of the cell in the circuit?
Q86 Two identical resistors connected in series have an equivalent resistance of 4 ohms. The same two resistors, when connected in parallel, have an equivalent resistance of
Q87 When three identical resistors are connected in series, their combined resistance is 6 Ω. What is their combined resistance when they are connected in parallel?
Q88 A physics student is given three 12-ohm resistors with instructions to create the circuit that would have the lowest possible resistance. The correct circuit would be a
Q89 In which circuit would ammeter A show the greatest current?
Q90 Three resistors, each of resistance 6 Ω, are arranged to give a 9 Ω combination across PQ. Which of the following is the arrangement?
Q91 Three networks X, Y and Z are shown below. Each resistor has the same resistance. Which list shows the network resistances in increasing order of magnitude?
Q92 The resistors in each of the circuits shown below each have the same resistance. Which of the following gives the circuits in order of increasing total resistance?
Structured Questions Bundle D
52:44
SQ22 (part 1) 4 cells and 3 resistors resistance and emf
SQ22 (part 2) 4 cells and 3 resistors current and charge
SQ22 (part 3) 4 cells and 3 resistors determining which cell will go flat first
SQ23 (part 1) Explanations question emf and output voltage
SQ23 (part 2) Explanations question why is low internal resistance important
SQ24 (part 1) Non-ohmic components semiconducting diode and filament lamp
SQ24 (part 2) Non-ohmic components resistance and power dissipated by a filament lamp
SQ25 (part 1) Thermistor question drawing the experimental setup
SQ25 (part 2) Thermistor question experimental procedure
SQ25 (part 3) Thermistor question pd across thermistor in a circuit
SQ25 (part 4) Thermistor question current in the circuit
SQ25 (part 15 Thermistor question resistance of fixed resistor
SQ25 (part 1) Thermistor question effect of the battery having internal resistance
SQ26 (part 1) Thermistor question 2 voltage across 540Ω resistor
SQ26 (part 2) Thermistor question 2 voltage across 1200Ω resistor and effective resistance of resistor and thermistor
SQ26 (part 3) Thermistor question 2 resistance of the thermistor
SQ26 (part 4) Thermistor question 2 effect of temperature on pd across 1200Ω resistor
SQ27 (part 1) Resistors W, X, Y and Z calculating total resistance from V and I
SQ27 (part 2) Resistors W, X, Y and Z other circuit calculations
SQ28 (part 1) Current-time graph for filament lamp determining maximum current from graph
SQ28 (part 2) Current-time graph for filament lamp resistance and power of lamp at normal operating temperature
SQ28 (part 3) Current-time graph for filament lamp explanation for decreasing current
SQ28 (part 4) Current-time graph for filament lamp changes to the current when connecting a second lamp to the supply
Structured Questions Bundle E
54:43
SQ29 (part 1) 9V battery with internal resistance calculating pd between points A and B
SQ29 (part 2) 9V battery with internal resistance energy transformed by battery and energy dissipated in internal resistance
SQ30 (part 1) Battery with internal resistance connected to variable resistor 3 explain why terminal pd decreases as current increases
SQ30 (part 2) Battery with internal resistance connected to variable resistor 3 finding ε from graph
SQ30 (part 3) Battery with internal resistance connected to variable resistor 3 finding r from graph
SQ30 (part 4) Battery with internal resistance connected to variable resistor 3 drawing new lines on the graph
SQ30 (part 5) Battery with internal resistance connected to variable resistor 3 circuit calculations
SQ31 (part 1) Battery with internal resistance connected in parallel to 2Ω resistor and R calculating pd
SQ31 (part 2) Battery with internal resistance connected in parallel to 2Ω resistor and R current and resistance
SQ31 (part 3) Battery with internal resistance connected in parallel to 2Ω resistor and R conservation of energy
SQ32 (part 1) Light-dependent resistor question current and voltage
SQ32 (part 2) Light-dependent resistor question changes in light intensity
SQ33 (part 1) Three resistors and thermistor calculating total resistance and current
SQ33 (part 2) Three resistors and thermistor voltage between different points
SQ34 (part 1) Lamps P and Q current in the battery
SQ34 (part 1) Lamps P and Q resistance of P and Q
SQ34 (part 1) Lamps P and Q series arrangement