1) Which of these is the symbol for a variable resistor? a) A b) B c) C d) D 2) Which of these diagrams shows an ammeter placed correctly to measure current through a resistor? a) A b) B c) C d) D 3) Which of these diagrams shows a voltmeter placed correctly to measure the potential difference across a resistor? a) A b) B c) C d) D 4) Which of these graphs best represents the characteristic graph for a resistor? a) A b) B c) C d) D 5) Which of these graphs best represents the characteristic graph for a bulb? a) A b) B c) C d) D 6) Why does the resistance of a bulb change with current? a) More current in the bulb means it has a lower resistance b) The bulb contains a fillament which gets hot, this increases its resistance c) The light leaving the bulb removes energy from the current, making it go down d) The resistance of a bulb does not change when the current changes 7) What would the voltmeter read in this circuit? a) 10 V b) 20 V c) 2.5 V d) 5 V 8) What would the value of the missing resistor need to be to be in this circuit? a) 10 Ohms b) 20 Ohms c) 30 Ohms d) 40 Ohms 9) What controls the resistance of an L.D.R.? a) Temperature b) Loudness c) Light d) Heat 10) Which component changes its resistance when temperature changes? a) Thermogram b) L.D.R. c) Variable resistor d) Thermistor 11) What would the resistance of a bulb be if the voltage across it was 20V and the current going through it was 5A a) 5Ω b) 10Ω c) 100Ω d) 4Ω 12) What would the voltage be across a 10Ω resistor if you measured a current of 2A going through it? a) 20V b) 8V c) 0.2V d) 5V 13) Which of these statements is true? a) Magnetic fields are only formed by moving currents b) A moving current will experience a force c) A moving current will generate a circular magnetic field around it d) Magnetic fields are the same as electrical fields 14) Which of these diagrams shows the direction of the magnetic field? a) A b) B c) C d) D 15) In flemming left-hand rule, what does the first finger represent? a) Field b) Force c) Current d) Motion 16) A wire is placed between the poles of a magnet. When a current passes through it the wires moves to the right. Which of these would reverse the direction of movement? a) Reversing the poles of the magnet b) Increasing the current c) Reversing the poles and switching the direction of the current d) none of the above 17) What does a commutator do in a motor? a) Fixes the power supply to the motors coil? b) Lets the motor turn c) Reverses the current in the coil as the motor turns over d) Makes the force on each side of the motor coil push in a different direction 18) Why do some motors have curved magnetic pole pieces? a) So the coil is kept at right angles to the field as it turns b) To make sure the magnetic field is as strong as possible near the coil c) So the coil can move smoothly around the axis d) To make the motor easier to make 19) Increasing the number of turns on a motors coil will... a) Increase the current b) Reduce the magnetic field c) Reduce the amount of wire needed to make the motor d) Increase the speed of the motor 20) When a magnet is moved in and out of a coil what happens? a) An alternating current is induced b) A direct current is induced c) A magnetic field is induced d) The coil will move

plenary 14.11

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