Questions and Answers
What is the unit of electric current?
Which of the following factors does NOT affect the electromotive force (emf) of a cell?
What does the internal resistance of a cell determine?
What is the definition of terminal potential difference?
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Which relationship correctly describes the maximum current from a cell?
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What is the effect of stronger electrolytes on the internal resistance of a cell?
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Which of the following describes the relationship between internal resistance and area of electrodes?
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Which of the following correctly defines lost volts?
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Study Notes
Current Electricity Overview
- Involves the flow of electrons or charges through a conductor.
- Electric current ( I ) measures the rate of electric charge flow in a circuit, represented by the formula: ( I = \frac{Q}{t} ) where ( Q ) is electric charge and ( t ) is time.
- Unit for current is the ampere (A), equivalent to ( \text{C s}^{-1} ).
Potential Difference and Electromotive Force
- Terminal potential difference (voltage) ( V ) represents the work done in moving a unit charge across two points in a circuit.
- Electromotive force (emf) ( E ) is the total work done per unit charge in a complete circuit: ( E = \frac{W}{Q} ) with ( W ) as work done.
- Voltage in a circuit not delivering current, or open circuit, is also described by emf.
- The unit of potential difference is the volt (V).
Factors Affecting Emf of a Cell
- Depends on the quality of chemicals or materials in the cell; stronger electrolytes result in lower internal resistance and greater emf.
- Influenced by the number of cells, time, and temperature; emf decreases with time and increasing temperature, such as in primary cells.
Internal Resistance
- Internal resistance ( r ) is the opposition to current flow caused by the cell producing the current.
- Determinants include:
- Nature of chemicals or electrodes.
- Amount and size of chemicals or electrodes.
- Area of electrodes; internal resistance is inversely proportional to area (( r \propto \frac{1}{A} )).
- Distance between electrodes; internal resistance is proportional to distance (( r \propto d )).
- Higher internal resistance limits the maximum current supplied by the cell, as described by the equation: ( I_{\text{max}} = \frac{E}{r} ).
Lost Volts and External Resistance
- Lost volt ( v ) refers to the potential difference across the internal resistance of a cell.
- External resistance ( R ) is the opposition encountered by current in a material, affecting the overall circuit performance.
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Description
This quiz covers the fundamental concepts of current electricity, including electric current, voltage, and the flow of charges in a conductor. It focuses on understanding the relationship between charge, current, and terminal potential difference. Test your knowledge on these essential electrical principles.
