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Electric circuits

4 dot points across 4 inquiry questions. Click any dot point for a focused answer with worked past exam questions where available.

How do components combine and why does a battery's voltage drop?

Series and parallel resistor combinations, Kirchhoff's two laws, EMF and internal resistance, and the relationship $\varepsilon = I(R + r)$ with terminal potential difference.
A focused answer to the Edexcel 9PH0 circuits content, covering series and parallel resistor rules, Kirchhoff's two laws, EMF and internal resistance, and terminal potential difference with the equation $\varepsilon = I(R + r)$ .
11 min answer →

What is electric current and how is energy transferred in a circuit?

Current as the rate of flow of charge, the equation $I = nAvq$ , potential difference and EMF as energy per unit charge, and electrical power and energy.
A focused answer to the Edexcel 9PH0 current and charge content, covering current as the rate of flow of charge, the equation $I = nAvq$ , potential difference and EMF, and electrical power and energy.
9 min answer →

How can we tap off a chosen fraction of a supply voltage?

The potential divider equation, the use of dividers to provide a variable potential difference, and sensor circuits using thermistors and LDRs.
A focused answer to the Edexcel 9PH0 potential divider content, covering the divider equation, variable dividers (potentiometers), and sensor circuits built from thermistors and light-dependent resistors.
10 min answer →

What determines the resistance of a component?

Ohm's law, I-V characteristics of ohmic and non-ohmic components, resistivity $\rho = RA/L$ , and the variation of resistance with temperature for metals and semiconductors.
A focused answer to the Edexcel 9PH0 resistance content, covering Ohm's law, I-V characteristics of a metallic conductor, filament lamp and diode, resistivity $\rho = RA/L$ , and temperature dependence in metals and semiconductors.
11 min answer →