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Questions and Answers
What does a voltmeter measure?
What does a voltmeter measure?
An ammeter is connected in parallel to measure current in a circuit.
An ammeter is connected in parallel to measure current in a circuit.
False
What component in a circuit is referred to as the load?
What component in a circuit is referred to as the load?
Appliance connected in a circuit
The substances which do not allow current to flow through them are called ______.
The substances which do not allow current to flow through them are called ______.
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Match the components to their functions:
Match the components to their functions:
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Which symbol is used to represent a fixed resistance?
Which symbol is used to represent a fixed resistance?
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Electrons flow from an uncharged conductor to a positively charged conductor.
Electrons flow from an uncharged conductor to a positively charged conductor.
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Describe the function of the key in an electric circuit.
Describe the function of the key in an electric circuit.
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What type of current is produced by pencil cells?
What type of current is produced by pencil cells?
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Secondary cells can provide large currents and can be recharged.
Secondary cells can provide large currents and can be recharged.
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What is the SI unit of electric current?
What is the SI unit of electric current?
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A cell providing direct current is represented by two vertical lines of __________ lengths.
A cell providing direct current is represented by two vertical lines of __________ lengths.
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Match the following cells to their characteristics:
Match the following cells to their characteristics:
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What happens when a key in a circuit is open?
What happens when a key in a circuit is open?
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Rheostats are used to increase the magnitude of current in a circuit.
Rheostats are used to increase the magnitude of current in a circuit.
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What is the conventional direction of current flow?
What is the conventional direction of current flow?
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Which direction does conventional current flow?
Which direction does conventional current flow?
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The electric current flows in the same direction as the flow of electrons.
The electric current flows in the same direction as the flow of electrons.
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What is the SI unit of potential difference?
What is the SI unit of potential difference?
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The resistance of a wire increases with an increase in __________.
The resistance of a wire increases with an increase in __________.
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According to Ohm’s law, resistance is calculated using which formula?
According to Ohm’s law, resistance is calculated using which formula?
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Match each factor affecting resistance with its relationship:
Match each factor affecting resistance with its relationship:
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The potential difference between two points is one volt if one joule of work is done to transfer one coulomb of charge.
The potential difference between two points is one volt if one joule of work is done to transfer one coulomb of charge.
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The use of compact fluorescent lights (CFL’s) can save up to __________ energy.
The use of compact fluorescent lights (CFL’s) can save up to __________ energy.
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Study Notes
Direct Current
- Regular pencil cells produce direct current (DC)
- DC is a constant magnitude current flowing in one direction
Kinds of Cells
Primary Cell
- Chemical reaction is irreversible
- Converts chemical energy into electrical energy
- Cannot be recharged
- Provides weak current
- Examples: Simple voltaic cell, Daniel cell
Secondary Cell
- Chemical reaction is reversible
- Converts electrical energy to chemical energy when current is passed
- Converts chemical energy to electrical energy when current is drawn
- Can be recharged
- Provides small or large currents
- Examples: Lead accumulator, Ni–Fe accumulator
Electric Current
- Charge (Q)
- Current (I) = Charge(Q) / Time(t)
- Scalar quantity
- SI unit is ampere (A)
- Conventionally, current direction is the flow of positive charge (opposite to electron flow)
Symbols in Circuit Diagrams
- Circuits have various components
- Current sources include AC or DC:
- AC: from mains or AC generator
- DC: from cell or battery
- A cell is represented by two vertical lines of unequal lengths
- When multiple cells are connected in series, they form a battery (cathode of one to the anode of the next)
Resistance Wire, Resistance Box, Rheostat, or Variable Resistance
- Resistance wire is made of an alloy (e.g., nichrome)
- Fixed resistance value (depends on length and thickness)
- Resistance box: has several standard resistances in series
- Rheostat: adjusts current magnitude (variable resistance)
- Fixed resistance is represented by R
- Rheostat (Variable resistance) represented by Rh
Ammeter
- Measures current magnitude
- Connected in series
Voltmeter
- Measures potential difference
- Connected in parallel
Galvanometer
- Measures small currents
- Measures direction of current flow
- Connected in series
Load
- Appliance connected in a circuit
- Represented by symbol L (e.g., bulb, heater)
Connecting Wires
- Connect electrical components
- Made of conductive materials (e.g., copper, aluminum)
Simple Electric Circuit
- Components: cell, key, bulb, ammeter, voltmeter, rheostat
- Key: completes/breaks circuit
- Bulb lights when key is closed, ammeter and voltmeter show readings
- Resistance changes with rheostat jockey, affect bulb brightness and readings
Insulators
- Do not allow current flow
- Low free electrons
- High resistance
Conductors
- Allow current flow
- Many free electrons
- Low resistance
Flow of Electrons
- Positively charged conductor to uncharged conductor: electron flow from uncharged to positive
- Negatively charged conductor to uncharged conductor: electron flow from negative to uncharged
- Positively charged conductor to negatively charged conductor: electron flow from negative to positive
Direction of Current Flow
- Conventional current: from higher to lower potential
- Electronic current: opposite to conventional current (electron flow)
Potential Difference (Voltage)
- Work done in transferring a unit positive charge between two conductors
- Scalar quantity, SI unit is volt (V)
- 1 volt: 1 joule of work to transfer 1 coulomb of charge
Electrical Resistance
- Obstruction to current flow in a conductor
- Ohm's Law: Resistance = Potential difference / Current (R = V/I)
Factors Affecting Resistance
- Length (R α l)
- Cross-sectional area (R α 1/A)
- Material (depends on atom arrangement and concentration)
- Temperature (ions vibrate more at higher temps, increasing resistance)
Efficient Use of Energy
- Reduce energy consumption and cost
- Examples: CFLs, better insulation, energy-efficient appliances, vehicle improvements, building design, etc.
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Description
Explore the fundamentals of electric circuits and the types of current in this quiz. Learn about direct current (DC), primary and secondary cells, and the basic concepts of electric charge and current flow. Test your understanding of circuit symbols and components.
