Paper 2 DC Circuits Drills

Q1 Series and parallel network

A $12.0\mathrm{V}$ supply is connected to a $4.0\Omega$ resistor in series with a parallel pair of $6.0\Omega$ and $3.0\Omega$.

1. Calculate the effective resistance of the parallel pair. [2]
2. Calculate total circuit current. [2]
3. Calculate p.d. across the $4.0\Omega$ resistor. [2]
4. Calculate current in the $3.0\Omega$ branch. [2]

Q2 Potential divider sensor

A $6.0\mathrm{V}$ supply is connected across a series pair: a fixed $2.0\mathrm{k\Omega }$ resistor on top and an NTC thermistor below. Output is measured across the thermistor. At one temperature the thermistor is $3.0\mathrm{k\Omega }$.

1. Calculate output p.d. [2]
2. State what happens to output p.d. when temperature increases. [2]
3. Explain why resistor position matters. [2]

Q3 Potentiometer

A uniform potentiometer wire of length $1.00\mathrm{m}$ has p.d. $2.00\mathrm{V}$ across it. A cell balances at length $0.720\mathrm{m}$.

1. Calculate the potential gradient. [1]
2. Calculate the cell emf. [2]
3. Explain why the null method avoids drawing current from the cell at balance. [2]