DC: Practical Circuits & Kirchhoff's Laws (CIE A Level Physics)

A cell of e .m .f. 2.0 V and negligible internal resistance is connected to a network of resistors as shown.

What is the current I ?

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?

 

	Current / A	External resistor value / Ω
A B C D	1.0 1.2 1.5 1.8	10.0 8.0 6.0 4.0

The diagram shows part of a current-carrying circuit. The ammeter has negligible resistance.

What is the reading on the ammeter ?

In the circuit shown, all the resistors are identical.

The reading on voltmeter V₁ is 8.0 V and the reading on voltmeter V₂ is 1.0 V. What are the readings on the other voltmeters?

 

	Reading on voltmeter V3 / V	Reading on voltmeter V4 / V
A B C D	1.5 3.0 4.5 6.0	1.0 2.0 3.0 4.0

A cell, two resistors of equal resistance and an ammeter are used to construct four circuits. The resistors are the only parts of the circuits that have resistance.

 In which circuit will the ammeter show the greatest reading ?

The diagram shows a circuit with four voltmeter readings V, V₁, V₂ and V₃.

Which equation relating the voltmeter readings must be true?

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 ?

When four identical resistors are connected as shown in diagram 1, the ammeter reads 1.0 A, and the voltmeter reads zero.

The resistors and meters are reconnected to the supply, as shown in diagram 2.

 What are the meter readings in diagram 2?

 

	Voltmeter reading / V	Ammeter reading / A
A B C D	0 3.0 3.0 6.0	1.0 0.5 1.0 0

The diagram shows currents I ₁, I ₂, I ₃, I ₄ and I ₅ in different branches of a circuit.

Which one of the following is correct?

In the circuit shown, all the resistors are identical and all the ammeters have negligible resistance.

The reading on ammeter A₁ is 0.6 A.

 What are the readings on the other ammeters?

 

	Reading on ammeter A2 / A	Reading on ammeter A3 / A	Reading on ammeter A4 / A
A B C D	1.0 1.4 1.8 2.2	0.3 0.6 0.9 1.2	0.1 0.2 0.3 0.4

A power supply of electromotive force (e .m .f.) 12 V and internal resistance 2 Ω is connected in series with a load resistor. The value of the load resistor is varied from 0.5 Ω to 4 Ω.

 Which graph shows how the power P dissipated in the load resistor varies with the resistance of the load resistor ?

Six resistors, each of resistance 5 Ω, are connected to a 2 V cell of negligible internal resistance.

What is the potential difference between terminals X and Y ?

A relay is required to operate 800 m from its power supply. The power supply has negligible internal resistance. The relay requires 16.0 V and a current of 0.60 A to operate.

 A cable connects the relay to the power supply, and two of the wires in the cable are used to supply power to the relay.

 The resistance of each of these wires is 0.0050 Ω per meter.

 What is the minimum output e .m .f. of the power supply ?

Four resistors of equal value are connected as shown.

How will the powers to the resistors change when resistor W is removed?

The diagram shows a four-terminal box connected to a battery and two ammeters.

The currents in the two meters are identical.

 Which circuit, within the box, will give this result ?

A p. d. of 12 V is connected between P and Q.

What is the p. d. between X and Y?

 

The diagram shows the circuit for a signal to display a green or a red light. It is controlled by the switch S.

The signal is some way from S to which it is connected by a cable with green, red and black wires. At the signal, the green and red wires are connected to the corresponding lamp and the black wire is connected to a terminal x to provide a common return. The arrangement is shown correctly connected and with the switch set to illuminate the red lamp.

 During maintenance, the wires at the signal are disconnected and, when reconnected, the black wire is connected in error to the green lamp (terminal g) instead of terminal x. The red wire is connected correctly to its lamp and connections at S remain as in the diagram.

When the system is tested with the switch connection to the red wire, what does the signal show ?

A box with four terminals P, Q, R and S contains two identical resistors.

When a battery of electromotive force (e .m. f.) E and negligible internal resistance is connected across PS, a high-resistance voltmeter connected across QR reads    

 Which diagram shows the correct arrangement of the two resistors inside the box ?

A 20 V d. c. supply is connected to a circuit consisting of five resistors L, M, N, P and Q.

There is a potential drop of 7 V across L and a further 4 V potential drop across N.

 What are the potential drops across M, P and Q?

 

	Potential drop across M / V	Potential drop across P / V	Potential drop across Q / V
A B C D	9 13 13 17	7 7 11 3	13 13 9 17

 

The diagram shows the electric motor for a garden pump connected to a 24 V power supply by an insulated two-core cable.

The motor does not work so, to find the fault, the negative terminal of a voltmeter is connected to the negative terminal of the power supply, and its other end is connected in turn to terminals X and Y at the motor.

 Which row represents two readings and a correct conclusion?

 

	Voltmeter reading when connected to X / V	Voltmeter reading when connected to Y / V	Conclusion
A B C D	24 24 24 24	0 12 24 24	break in positive wire of cable break in negative wire of cable break in connection within the motor break in negative wire of cable