1. Learning objectives What is an electrical circuit? Electrical quantity
Charge
Current
Voltage
Resistance

2. What is an electric circuit?
An electric circuit is an interconnection of electrical elements.

3. Charge (q)
We experience effect of charge when remove wool sweater and we see sparks!
Atoms have electrons, protons, and neutrons.
Electron has negative charge.
Proton has positive charge.
Neutron does not have charge.

4. Current (i) Electric current is the flow of electric charge.
Current is measured in amperes (A).
1 ampere = 1 coulomb/second

5. Multiple and Submultiple Units
Units of Current
The basic unit of current is the ampere (A).
Submultiple units of current are:
milliampere (mA) 1-thousandth of an ampere or 10-3 A
microampere (μA) 1-millionth of an ampere or 10-6 A

6. Electric circuit

7. Learning objectives What is an electrical circuit? Electrical quantity
Charge
Current
Voltage
Resistance

8. Voltage (v)
To move the electrons, requires some work or energy transfer.
Voltage is the “pressure” which causes charges to flow.
Drinking with straw analogy
Juice = Charge
Air pressure using mouth = Voltage
Flow of juice = Current
Straw = Wire
Courtesy: ktuos.deviantart.com

9. Voltage of Battery Voltage is measured between two points.
Positive terminal  1.5 volt
Negative or Ground terminal  0 volt
Voltage across the battery is 1.5 – 0 = 1.5 volt
Courtesy:

10. Voltage and Current Voltage do not move, it is a force.
Electrons move, which is current.

11. Voltage
Electric voltage is always across the circuit element or between two points in a circuit. a b Vb Va
Vab = Va - Vb

12. Remember! i Vab Voltage is always across an element
Current is through an element
Current flows from higher V to lower V. i a b
Vab

13. Voltage polarity + Va = 16 V Vab = 6V - Vb = 10 V Vab = 6V Va > Vb
There is a 6V voltage drop from a to b
Vab = 6V
There is a 6V voltage rise from b to a

14. Multiple and Submultiple Units
Units of Voltage
The basic unit of voltage is the volt (V).
Multiple units of voltage are:
kilovolt (kV) 1 thousand volts or 103 V
megavolt (MV) 1 million volts or 106 V
Submultiple units of voltage are:
millivolt (mV) 1-thousandth of a volt or 10-3 V
microvolt (μV) 1-millionth of a volt or 10-6 V

15. The Open Circuit
When a current path is broken (incomplete) the circuit is said to be open. There is no current in an open circuit.
An open circuit
(no current is flowing)
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

16. The Closed Circuit
A circuit can be defined as a path for current flow. Any circuit has three key characteristics:
1. There must be a source of potential difference (voltage). Without voltage current cannot flow.
2. There must be a complete path for current flow.
3. The current path normally has resistance, either to generate heat or limit the amount of current.

17. The Closed Circuit A closed circuit (current is flowing)
The purpose of the
resistor is to limit
current (flow) or to
generate heat.
A closed circuit
(current is flowing)
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

18. The Short Circuit
When the current path is closed but has little or no resistance, the result is a short circuit. Short circuits can result in too much current.
An short circuit
(high current is flowing, do not do this!)
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

19. Learning objectives What is an electrical circuit? Electrical quantity
Charge
Current
Voltage
Resistance

20. Resistance (R) is Opposition to Current
Juice = Charge
Air pressure using mouth = Voltage
Flow of juice = Current
Straw = Wire
Pressing straw by hand = Resistance
(a)
Fig. 1-10: (a) photograph of resistors. (b) Schematic symbol for any type of fixed resistor.
Courtesy: ktuos.deviantart.com
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

21. Multiple and Submultiple Units
Units of Resistance
The basic unit of resistance is the Ohm (Ω).
Multiple units of resistance are:
kilohm (kΩ) 1 thousand ohms or 103 Ω
Megohm (MΩ) 1 million ohms or 106 Ω

22. The Digital Multimeter
A digital multimeter (DMM) is a device used to measure the voltage, current, or resistance in a circuit.
Fig. 1-16: A handheld digital multimeter and a benchtop unit.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

23. Video Tutorial on DMM