Question 1
Each of the resistors in the circuit below has a resistance R Ohms. What is their total resistance (in terms of R).
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Question 2
a)
| Four identical resistors are connected to a battery of emf 12V and zero internal resistance, as shown below. | ||||||||
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| What voltage would a voltmeter read when connected across the following points? | |||||||||
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b)
| A short circuit (a wire of very low resistance) is connected across points C and D, as shown below. | ||||||||
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| What voltage would a voltmeter now read when connected across the following points? | |||||||||
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Question 3
a)
| Calculate the total resistance of the four resistors in the circuit shown below. |
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b)
| Calculate the total resistance of the same four resistors when a wire of very low resistance is connected across points X and Y. |
Questions 4 to 11 are all about the circuit drawn below. The cell has zero internal resistance
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Question 5 Calculate the current I.
Question 6 Calculate the voltage across the points A and B.
Question 7 Calculate the current I1.
Question 8 How much charge will pass through the cell in 20s?
Question 9 How much energy will be converted to heat by the 6
resistor in 5 minutes?Question 10 Calculate the power dissipated in the 8
resistor.Question 11 Calculate the total amount of energy converted to heat by all the resistors in 10 minutes
Question 12
| Calculate the maximum current which can be supplied by each of the following batteries | |
| a) | a car battery of emf  = 13·2V and internal resistance r = 0·15 |
| b) | a battery of eight cells each of emf = 1·6V and internal resistance r = 0·4 |
| Two resistors, R1 = 3 and R2 = 6, are connected in parallel with each other. They are then connected to a battery of emf, =10V and internal resistance r = 3. | ||
| Calculate | a) | the current flowing through the battery |
| b) | the current flowing through the 6 resistor. | |
A battery of emf,
= 6V is connected to two 5 resistors in parallel with each other. If the current flowing through the battery is 2 A, calculate the internal resistance of the battery. |
| Three 12 resistors are to be connected to a battery of = 24V and r = 2. Draw circuit diagrams showing how the resistors should be connected in order that the current flowing through the battery is | ||||
| a) 4A | b) 1·2A | c) 0·63A | d) 2·4A | |
| This question is about rms currents and voltages. | |
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| For the circuit shown above calculate | |
| a) | the rms value of the current, I |
| b) | the maximum value of the current |
| c) | the mean power dissipated in R1 |
| d) | the rms value of the voltage across R2. |
A resistor is to be made using wire of diameter 0.2mm. The wire is made of nichrome of resistivity 1.50×10-6
 m. | |
a)
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Calculate the length of wire needed to make a resistor of resistance 15.0
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b)
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If the diameter of the wire was measured using a Vernier calliper having a precision of ±0.02mm what is the uncertainty in the value of the resistance made using the wire (state your answer in the usual way: resistance = R ±
 R ). Ignore any other sources of uncertainty in this calculation. |
c)
| Calculate the power dissipated in the resistor when a current of 1.5A flows through it. |
| d) | The resistor is found to change temperature by 2.4°CW-1 of power dissipated. After the current (1.5A) has been flowing for a few minutes, the temperature of the resistor will have increased. Given that the temperature coefficient of resistance of nichrome is 4.0×10−4°C-1, show that the change in resistance of the resistor is unlikely to cause too many problems. |
A thermistor, Rt (temperature dependent resistor) is to be used in a potential divider circuit as part of a thermostat. The heater is switched on (by circuits not shown) when the voltage across Rt is 1.25V. The graph shows the variation with temperature of the resistance of Rt.
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Find the approximate temperature at which the heater will switch on
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a)
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with R = 9k
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b)
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with R = 18k
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