BackThree ideal transformers A, B, and C have the same primary voltage but different turns ratios: transformer A has a turns ratio of = , transformer B has = , and transformer C has = . Rank the transformers in order of decreasing rms secondary voltage.
(II) For the electric power transmission system shown in Fig. 29–26, what is the ratio Ns/Np for (a) the step-up transformer, (b) the step-down transformer next to the home?
Which of the following statements about transformers is correct?
A model-train transformer plugs into 120-V ac and draws 0.35 A while supplying 6.5 A to the train.
(a) What voltage is present across the tracks?
(b) Is the transformer step-up or step-down?
In a transformer, what is the primary cause of voltage being induced in the secondary coil?
Which device is used to transfer from one electric circuit to another by electromagnetic induction?
How are step-up transformers used in the transmission of electrical energy over long distances?
In a step-down transformer, which quantity is reduced from the side to the side?
Which of the following types of transformer is used to step voltage up for transmission?
A high-intensity desk lamp is rated at 35 W but requires only 12 V. It contains a transformer that converts 120-V household voltage.
(c) What is the current in the primary coil?
(d) What is the resistance of the bulb when on?
Electricity is distributed from electrical substations to neighborhoods at 15,000 V. This is a 60 Hz oscillating (AC) voltage. Neighborhood transformers, seen on utility poles, step this voltage down to the 120 V that is delivered to your house. No energy is lost in an ideal transformer, so the output power Pout from the secondary coil equals the input power Pin to the primary coil. Suppose a neighborhood transformer delivers 250 A at 120 V. What is the current in the 15,000 V line from the substation?
A transformer has 680 turns in the primary coil and 85 in the secondary coil. What kind of transformer is this, and by what factor does it change the voltage? By what factor does it change the current?
Electricity is distributed from electrical substations to neighborhoods at 15,000 V. This is a 60 Hz oscillating (AC) voltage. Neighborhood transformers, seen on utility poles, step this voltage down to the 120 V that is delivered to your house. a. How many turns does the primary coil on the transformer have if the secondary coil has 100 turns?
A Step-Down Transformer. A transformer connected to a 120 V (rms) ac line is to supply 12.0 V (rms) to a portable electronic device. The load resistance in the secondary is 5.00 Ω. What should the ratio of primary to secondary turns of the transformer be?
A high-intensity desk lamp is rated at 35 W but requires only 12 V. It contains a transformer that converts 120-V household voltage.
(a) Is the transformer step-up or step-down?
(b) What is the current in the secondary coil when the lamp is on?