Electromotive Force & Internal Resistance (AQA AS Physics)

A battery of e.m.f. 12 V and internal resistance 2.0 Ω is connected in series with an ammeter of negligible resistance and an external resistor. External resistors of various different values are used.

Which combination of current and resistor value is not correct?

A simple circuit is formed by connecting a resistor of resistance R between the terminals of a battery of electromotive force (e.m.f.) 9.0 V and constant internal resistance r.

A charge of 6.0 C flows through the resistor in a time of 2.0 minutes, causing it to dissipate 48 J of thermal energy. 

What is the internal resistance r of the battery?

A student found two unmarked resistors. To determine the resistance of the resistors, the circuit below was set up. The resistors were connected in turn between P and Q, noting the current readings.

The voltage readings were noted without the resistors and with each resistor in turn.

The results were entered into a spreadsheet, as shown.

The student forgot to enter the column headings.

Which order of the headings would be correct?

A battery, with a constant internal resistance, is connected to a resistor of resistance 250 Ω, as shown.

The current in the resistor is 40 mA for a time of 60 s. During this time 6.0 J of energy is lost in the internal resistance.

What is the energy supplied to the external resistor during the 60 s and the e.m.f. of the battery?

A battery with e.m.f. E and internal resistance r is connected in series with an external variable resistor.

The value of the external resistance R is slowly increased from zero.

Which statement is correct? (Ignore any temperature effects.)

Three cells each have an e.m.f. ε = 1.2 V and an internal resistance r = 0.8 Ω.

Which combination of these cells will deliver a total e.m.f. of 1.2 V and a maximum current of 4.5 A?

A battery is connected to a 20 Ω resistor and a switch in series. A voltmeter is connected across the battery.

When the switch is open the voltmeter reads 3.82 V. When the switch is closed the reading is 3.35 V.

What is the internal resistance of the battery?

A cell of emf ε and internal resistance r is connected to an external load of resistance R as shown.

Which of the following statements is incorrect?

A circuit is set up such that a cell of emf E and internal resistance r is connected to a variable resistor R. 

The load resistance R is varied such that a graph of the quantity IR can be plotted against the current I, using readings from the ammeter.

Which row, A to D, gives the correct values for the emf E of the cell, its internal resistance r and the power dissipated in the load resistance when the current is 1.5 A,  ?

A cell of emf E and internal resistance r is connected to a load resistor R as shown:

Pairs of values for the reading on the voltmeter V and R is given:

What is the internal resistance of the cell?

A battery of electromotive force ε delivers charge Q to the load resistance.

Which of the following statements is correct?

Two cells, X and Y, of emf and internal resistance ,   and ,  respectively, are connected in turn to a variable resistor R.

The emf of cell Y is 50% the emf of cell X.

Which expression gives the terminal potential difference V that equalises the current in both circuits?

A cell of emf E and internal resistance r is connected to a variable resistor R.

Which of the following statements about the circuit is / are correct?

1. If the resistance of R decreases, the terminal potential difference also decreases but the power dissipated in the cell is large
2. If the resistance of R is very large, the current in the circuit is very small but most of the power supplied by the cell is dissipated by R
3. If the resistance of R is very large, the power dissipated in R tends towards the value 

A 10 V supply with an unknown internal resistance r is connected to two 25 kΩ resistors as shown.

A non-ideal voltmeter, of resistance 100 kΩ, is connected in parallel with one of the resistors.

What is the internal resistance of the supply if the voltmeter reads 4.0 V?

A cell of emf E and internal resistance r is connected to a variable load resistance, R. 

Which of the following graphs correctly shows how the power dissipated across the load resistance  varies with load resistance R?

Two lamps, L₁ and L₂, of resistance 11 Ω and 22 Ω respectively, are connected in turn in series and in parallel to a cell with emf 40 V and internal resistance 7 Ω.

Which lamp(s) shine(s) the brightest?  

A circuit is designed to measure the emf of a cell E which has an internal resistance of 0.75 Ω (you may assume the 2.0 V cell is of negligible resistance). 

There is zero current in E when the variable resistor is set at 3.0 Ω.

What is the emf of cell E?

A uniform wire of length 110 cm and radius 0.55 mm is attached between X and Y in series with a cell of emf 3.0 V and internal resistance 0.80 Ω.

The wire has a resistivity of 1.1 × 10^–6 Ω m^–1.

A cell C of emf 1.5 V and internal resistance 0.50 Ω is also connected to the circuit, with a moveable contact J which can be connected to any point along XY.  

How far from X is the moveable contact J when there is no current through the cell C?

Which of the following rows, A to D, is not a possible set of values for the emf ε and internal resistance r of a cell with the current I through it?  

Which of the following statements most accurately explains the electromotive force of a cell?