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Questions and Answers
What is the definition of electromotive force (e.m.f)?
What is the definition of electromotive force (e.m.f)?
- The resistance within a power supply
- The amount of electrical energy converted to chemical energy per coulomb of charge
- The amount of chemical energy converted to electrical energy per coulomb of charge (correct)
- The force applied to charge by a battery
How is electromotive force (e.m.f) represented?
How is electromotive force (e.m.f) represented?
- Δ
- µ
- ε (correct)
- σ
Why does a cell become warm after a period of time?
Why does a cell become warm after a period of time?
- Due to the increase in internal resistance
- Due to the discharge of electricity (correct)
- Due to the decrease in internal resistance
- Due to the conversion of electrical energy to chemical energy
How is e.m.f measured using a voltmeter?
How is e.m.f measured using a voltmeter?
What happens to the voltage over time in a power supply due to internal resistance?
What happens to the voltage over time in a power supply due to internal resistance?
How can a cell be conceptually viewed in terms of e.m.f and internal resistance?
How can a cell be conceptually viewed in terms of e.m.f and internal resistance?
What does the terminal potential difference represent in a cell?
What does the terminal potential difference represent in a cell?
What would happen to the terminal p.d if a cell had no internal resistance?
What would happen to the terminal p.d if a cell had no internal resistance?
What is the definition of 'lost volts' in a cell due to internal resistance?
What is the definition of 'lost volts' in a cell due to internal resistance?
Which equation represents 'lost volts' in a cell according to Ohm's law?
Which equation represents 'lost volts' in a cell according to Ohm's law?
Why is the terminal p.d always lower than the e.m.f in a cell?
Why is the terminal p.d always lower than the e.m.f in a cell?
What does 'lost volts' represent in a cell circuit?
What does 'lost volts' represent in a cell circuit?
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Study Notes
Electromotive Force (e.m.f)
- Defined as the energy per unit charge supplied by a cell or battery in an electrical circuit.
- Represented by the symbol E and measured in volts (V).
Cell Heating
- A cell generates heat after prolonged use due to internal resistance, leading to energy dissipation.
Measuring e.m.f
- To measure e.m.f, a voltmeter is connected across the terminals of a cell without drawing current, ensuring an accurate reading of potential difference.
Voltage and Internal Resistance
- Over time, the voltage in a power supply decreases due to internal resistance causing a voltage drop as current flows.
Conceptual View of a Cell
- A cell can be viewed as having an electromotive force (e.m.f) and an internal resistance, which together influence the performance of the cell in a circuit.
Terminal Potential Difference (p.d)
- Terminal p.d represents the voltage available at the cell terminals when current flows, reflecting the effective energy supplied to the external circuit.
Impact of No Internal Resistance
- If a cell had no internal resistance, the terminal potential difference would equal the e.m.f, resulting in maximum efficiency in voltage delivery.
Lost Volts
- 'Lost volts' refers to the voltage drop that occurs within the cell due to internal resistance when current flows.
Equation for Lost Volts
- According to Ohm's law, lost volts is calculated as ( I \times r ), where I is the current and r is the internal resistance.
Terminal p.d vs. e.m.f
- The terminal potential difference is always lower than the e.m.f because of energy lost to internal resistance when current is drawn.
Significance of Lost Volts
- 'Lost volts' represent the energy wasted in overcoming internal resistance, indicating inefficiencies within the circuit.
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