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QLDPhysicsQuick questions
Unit 1: Thermal, nuclear and electrical physics
Quick questions on Electric current, potential difference and Ohm's law (QCE Physics Unit 1)
10short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.
What is electric current?Show answer
The rate of flow of electric charge:
What is potential difference?Show answer
The work done per unit charge moved between two points:
What is resistance?Show answer
The opposition to current flow:
What is calling current the speed of electrons?Show answer
Drift speed of electrons in a wire is fractions of a millimetre per second. Current is the rate of charge flow, not the speed of charges.
What is treating non-ohmic devices as ohmic?Show answer
A filament lamp draws less than proportional current at high voltages because it heats up. The fixed $R$ assumption fails.
What is mixing up volt and joule per coulomb when calculating energy?Show answer
Energy per charge is $V$, total energy is $V Q$, total energy per second is $VI$. Get the multiplication right.
What is forgetting the direction convention?Show answer
QCAA uses conventional current (positive charge direction). Electron flow is in the opposite direction.
What is iA1?Show answer
Often an ohm-meter reading or an unseen I-V graph asking for the resistance at a stated point and whether the device is ohmic.
What is eA Paper 1?Show answer
Multiple choice on the units, the formula, and identifying ohmic from non-ohmic shapes.
What is eA Paper 2?Show answer
Combined with the power-and-energy and series-and-parallel dot points to find unknown resistors or currents in a small circuit.